radeon kms: do not flush uninitialized hotplug work

Fix a warning from lockdep caused by calling flush_work() for
uninitialized hotplug work. Initialize hotplug_work, audio_work
and reset_work upon successful radeon_irq_kms_init() completion
and thus perform hotplug flush_work only when rdev->irq.installed
is true.

[    4.790019] [drm] Loading CEDAR Microcode
[    4.790943] r600_cp: Failed to load firmware "radeon/CEDAR_smc.bin"
[    4.791152] [drm:evergreen_startup] *ERROR* Failed to load firmware!
[    4.791330] radeon 0000:01:00.0: disabling GPU acceleration

[    4.792633] INFO: trying to register non-static key.
[    4.792792] the code is fine but needs lockdep annotation.
[    4.792953] turning off the locking correctness validator.

[    4.793114] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 3.11.0-rc0-dbg-10676-gfe56456-dirty #1816
[    4.793314] Hardware name: Acer             Aspire 5741G    /Aspire 5741G    , BIOS V1.20 02/08/2011
[    4.793507]  ffffffff821fd810 ffff8801530b9a18 ffffffff8160434e 0000000000000002
[    4.794155]  ffff8801530b9ad8 ffffffff810b8404 ffff8801530b0798 ffff8801530b0000
[    4.794789]  ffff8801530b9b00 0000000000000046 00000000000004c0 ffffffff00000000
[    4.795418] Call Trace:
[    4.795573]  [<ffffffff8160434e>] dump_stack+0x4e/0x82
[    4.795731]  [<ffffffff810b8404>] __lock_acquire+0x1a64/0x1d30
[    4.795893]  [<ffffffff814a87f0>] ? dev_vprintk_emit+0x50/0x60
[    4.796034]  [<ffffffff810b8fb4>] lock_acquire+0xa4/0x200
[    4.796216]  [<ffffffff8106cd75>] ? flush_work+0x5/0x280
[    4.796375]  [<ffffffff8106cdad>] flush_work+0x3d/0x280
[    4.796520]  [<ffffffff8106cd75>] ? flush_work+0x5/0x280
[    4.796682]  [<ffffffff810b659d>] ? trace_hardirqs_on_caller+0xfd/0x1c0
[    4.796862]  [<ffffffff8131d775>] ? delay_tsc+0x95/0xf0
[    4.797024]  [<ffffffff8141bb8b>] radeon_irq_kms_fini+0x2b/0x70
[    4.797186]  [<ffffffff814557c9>] evergreen_init+0x2a9/0x2e0
[    4.797347]  [<ffffffff813ebb1f>] radeon_device_init+0x5ef/0x700
[    4.797511]  [<ffffffff81335bc7>] ? pci_find_capability+0x47/0x50
[    4.797672]  [<ffffffff813edaed>] radeon_driver_load_kms+0x8d/0x150
[    4.797843]  [<ffffffff813ce426>] drm_get_pci_dev+0x166/0x280
[    4.798007]  [<ffffffff8116cff5>] ? kfree+0xf5/0x2e0
[    4.798168]  [<ffffffff813ea298>] ? radeon_pci_probe+0x98/0xd0
[    4.798329]  [<ffffffff813ea2aa>] radeon_pci_probe+0xaa/0xd0
[    4.798489]  [<ffffffff81339404>] pci_device_probe+0x84/0xe0
[    4.798644]  [<ffffffff814ac7d6>] driver_probe_device+0x76/0x240
[    4.798805]  [<ffffffff814aca73>] __driver_attach+0x93/0xa0
[    4.798948]  [<ffffffff814ac9e0>] ? __device_attach+0x40/0x40
[    4.799126]  [<ffffffff814aa82b>] bus_for_each_dev+0x6b/0xb0
[    4.799272]  [<ffffffff814ac2be>] driver_attach+0x1e/0x20
[    4.799434]  [<ffffffff814abec0>] bus_add_driver+0x1f0/0x280
[    4.799596]  [<ffffffff814ad0e4>] driver_register+0x74/0x150
[    4.799758]  [<ffffffff8133923d>] __pci_register_driver+0x5d/0x60
[    4.799936]  [<ffffffff81d16efc>] ? ttm_init+0x67/0x67
[    4.800081]  [<ffffffff813ce655>] drm_pci_init+0x115/0x130
[    4.800243]  [<ffffffff81d16efc>] ? ttm_init+0x67/0x67
[    4.800405]  [<ffffffff81d16f98>] radeon_init+0x9c/0xba
[    4.800586]  [<ffffffff810002ca>] do_one_initcall+0xfa/0x150
[    4.800746]  [<ffffffff81073f60>] ? parse_args+0x120/0x330
[    4.800909]  [<ffffffff81cdafae>] kernel_init_freeable+0x111/0x191
[    4.801052]  [<ffffffff81cda87a>] ? do_early_param+0x88/0x88
[    4.801233]  [<ffffffff815fb670>] ? rest_init+0x140/0x140
[    4.801393]  [<ffffffff815fb67e>] kernel_init+0xe/0x180
[    4.801556]  [<ffffffff8160dcac>] ret_from_fork+0x7c/0xb0
[    4.801718]  [<ffffffff815fb670>] ? rest_init+0x140/0x140

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org