[media] cx24123: fix kernel oops due to missing parent pointer

When I try to set the TV standard to e.g. PAL on my Hauppauge WinTV-HVR3000 I get
the following oops:

 9464.262345] CX24123: detected CX24123
[ 9464.262526] BUG: unable to handle kernel NULL pointer dereference at 0000000000000230
[ 9464.262555] IP: [<ffffffff816676b5>] acpi_i2c_install_space_handler+0x15/0xc0
[ 9464.262576] PGD 0
[ 9464.262584] Oops: 0000 [#1] PREEMPT SMP
[ 9464.262597] Modules linked in: cx24123 cx22702 cx88_dvb(+) videobuf_dvb cx88_vp3054_i2c cx88_blackbird cx8802 ir_lirc_codec ir_xmp_decoder ir_sanyo_decoder ir_jvc_decoder ir_mce_kbd_decoder ir_sharp_decoder lirc_dev ir_sony_decoder ir_rc6_decoder ir_nec_decoder ir_rc5_decoder rc_hauppauge wm8775 tuner_simple tuner_types tda9887 cx8800 cx88xx btcx_risc videobuf_dma_sg videobuf_core mt2131 s5h1409 tda8290 tuner cx25840 cx23885 altera_ci tda18271 altera_stapl videobuf2_dvb tveeprom cx2341x videobuf2_dma_sg dvb_core rc_core videobuf2_memops videobuf2_core v4l2_common videodev media nouveau x86_pkg_temp_thermal cfbfillrect cfbimgblt cfbcopyarea ttm drm_kms_helper processor button isci
[ 9464.262786] CPU: 2 PID: 2417 Comm: modprobe Not tainted 3.17.0-rc1-telek #322
[ 9464.262796] Hardware name: ASUSTeK COMPUTER INC. Z9PE-D8 WS/Z9PE-D8 WS, BIOS 5404 02/10/2014
[ 9464.262807] task: ffff881097959ad0 ti: ffff88109967c000 task.ti: ffff88109967c000
[ 9464.262817] RIP: 0010:[<ffffffff816676b5>]  [<ffffffff816676b5>] acpi_i2c_install_space_handler+0x15/0xc0
[ 9464.262834] RSP: 0018:ffff88109967fbd8  EFLAGS: 00010246
[ 9464.262843] RAX: 0000000000000000 RBX: ffff880892a89540 RCX: 0000000000000000
[ 9464.262853] RDX: 0000000080000001 RSI: ffff880892e75870 RDI: ffff880892a89540
[ 9464.262862] RBP: ffff88109967fbf8 R08: ffff881099b2ccc0 R09: ffff880891efa088
[ 9464.262872] R10: 0000000000000000 R11: 0000000000000022 R12: 0000000000000000
[ 9464.262883] R13: ffff880892a895b0 R14: 00000000ffffffed R15: ffff88089b48f800
[ 9464.262893] FS:  00007fe42b6d7700(0000) GS:ffff88089fc40000(0000) knlGS:0000000000000000
[ 9464.262904] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 9464.262912] CR2: 0000000000000230 CR3: 0000001094078000 CR4: 00000000000407e0
[ 9464.262922] Stack:
[ 9464.262927]  ffff880892a89540 0000000000000000 ffff880892a895b0 ffff88109a155a80
[ 9464.262944]  ffff88109967fc20 ffffffff81666a36 0000000000000020 ffff880892a89540
[ 9464.262960]  ffffffffa01c8d40 ffff88109967fc40 ffffffff81666c67 ffff880892a89000
[ 9464.262977] Call Trace:
[ 9464.262987]  [<ffffffff81666a36>] i2c_register_adapter+0x166/0x340
[ 9464.262998]  [<ffffffff81666c67>] i2c_add_adapter+0x57/0x60
[ 9464.263011]  [<ffffffffa01e2c58>] cx24123_attach+0x108/0x1ba [cx24123]
[ 9464.263025]  [<ffffffffa01c5a76>] dvb_register+0x404/0x245b [cx88_dvb]
[ 9464.263039]  [<ffffffffa0059183>] ? videobuf_queue_core_init+0xe3/0x140 [videobuf_core]
[ 9464.263052]  [<ffffffffa01c54b1>] cx8802_dvb_probe+0x1e1/0x261 [cx88_dvb]
[ 9464.263066]  [<ffffffffa01a3b00>] cx8802_register_driver+0x190/0x20d [cx8802]
[ 9464.263077]  [<ffffffffa01cc000>] ? 0xffffffffa01cc000
[ 9464.263089]  [<ffffffffa01cc025>] dvb_init+0x25/0x27 [cx88_dvb]
[ 9464.263101]  [<ffffffff810002c4>] do_one_initcall+0x84/0x1c0
[ 9464.263113]  [<ffffffff811893fa>] ? __vunmap+0x9a/0x100
[ 9464.263125]  [<ffffffff81122a66>] load_module+0x1216/0x1790
[ 9464.263134]  [<ffffffff8111ff70>] ? __symbol_put+0x70/0x70
[ 9464.263145]  [<ffffffff811aa8cc>] ? vfs_read+0x11c/0x170
[ 9464.263156]  [<ffffffff811201d9>] ? copy_module_from_fd.isra.53+0x119/0x170
[ 9464.263168]  [<ffffffff81123116>] SyS_finit_module+0x76/0x80
[ 9464.263181]  [<ffffffff818d19e9>] system_call_fastpath+0x16/0x1b
[ 9464.263190] Code: 81 31 c0 e8 2e f6 e8 ff 48 83 c4 08 5b 5d eb de 66 0f 1f 44 00 00 55 48 89 e5 41 56 41 55 41 54 53 41 be ed ff ff ff 48 8b 47 70 <48> 8b 80 30 02 00 00 48 85 c0 74 58 4c 8b 68 08 4d 85 ed 74 4f
[ 9464.263347] RIP  [<ffffffff816676b5>] acpi_i2c_install_space_handler+0x15/0xc0
[ 9464.263361]  RSP <ffff88109967fbd8>
[ 9464.263367] CR2: 0000000000000230
[ 9464.266919] ---[ end trace 57fd490bdb72e733 ]---

I traced this to a NULL i2c_adapter parent pointer when cx24123 creates its own
i2c adapter. The acpi_i2c_install_space_handler function appeared in 3.17, so
that's probably why this hasn't been seen before.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>