mtd cs553x_nand: Initialise ecc.strength before nand_scan()

Loading cs553x_nand with Hynix H27U1G8F2BTR NAND flash causes this bug:

kernel BUG at drivers/mtd/nand/nand_base.c:3345!
invalid opcode: 0000 [#1]
Modules linked in: cs553x_nand(+) vfat fat usb_storage ehci_hcd usbcore usb_comr
Pid: 436, comm: modprobe Not tainted 3.6.7 #1
EIP: 0060:[<c118d205>] EFLAGS: 00010296 CPU: 0
EIP is at nand_scan_tail+0x64c/0x69c
EAX: 00000034 EBX: cea6ed98 ECX: 00000000 EDX: 00000000
ESI: cea6ec00 EDI: cea6ec00 EBP: 20000000 ESP: cdd17e48
 DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068
CR0: 8005003b CR2: 0804e119 CR3: 0d850000 CR4: 00000090
DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
DR6: ffff0ff0 DR7: 00000400
Process modprobe (pid: 436, ti=cdd16000 task=cdd1c320 task.ti=cdd16000)
Stack:
 c12e962c c118f7ef 00000003 cea6ed98 d014b25c 20000000 fffff007 00000001
 00000000 cdd53b00 d014b000 c1001021 cdd53b00 d01493c0 cdd53b00 cdd53b00
 d01493c0 c1047f83 d014b4a0 00000000 cdd17f9c ce4be454 cdd17f48 cdd1c320
Call Trace:
 [<c118f7ef>] ? nand_scan+0x1b/0x4d
 [<d014b25c>] ? init_module+0x25c/0x2de [cs553x_nand]
 [<d014b000>] ? 0xd014afff
 [<c1001021>] ? do_one_initcall+0x21/0x111
 [<c1047f83>] ? sys_init_module+0xe4/0x1261
 [<c1031207>] ? task_work_run+0x36/0x43
 [<c1265ced>] ? syscall_call+0x7/0xb
Code: fa ff ff c7 86 d8 00 00 00 01 00 00 00 e9 5f fc ff ff 68 f8 26 2e c1 e8 a7
EIP: [<c118d205>] nand_scan_tail+0x64c/0x69c SS:ESP 0068:cdd17e48

Initialising ecc.strength before the call to nand_scan() fixes this.

Signed-off-by: Nathan Williams <nathan@traverse.com.au>
Cc: stable@vger.kernel.org [3.4+]
Acked-by: Brian Norris <computersforpeace@gmail.com>
Acked-by: Mike Dunn <mikedunn@newsguy.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>