mtd: nand: mxc: fix obiwan error in mxc_nand_v[12]_ooblayout_free() functions

mtd: nand: mxc: fix obiwan error in mxc_nand_v[12]_ooblayout_free() functions

commit a894cf6c5a82 ("mtd: nand: mxc: switch to mtd_ooblayout_ops")
introduced a regression accessing the OOB area from the mxc_nand
driver due to an Obiwan error in the mxc_nand_v[12]_ooblayout_free()
functions. They report a bogus oobregion { 64, 7 } which leads to
errors accessing bogus data when reading the oob area.

Prior to the commit the mtd-oobtest module could be run without any
errors. With the offending commit, this test fails with results like:
|Running mtd-oobtest
|
|=================================================
|mtd_oobtest: MTD device: 5
|mtd_oobtest: MTD device size 524288, eraseblock size 131072, page size 2048, count of eraseblocks 4, pages per eraseblock 64, OOB size 64
|mtd_test: scanning for bad eraseblocks
|mtd_test: scanned 4 eraseblocks, 0 are bad
|mtd_oobtest: test 1 of 5
|mtd_oobtest: writing OOBs of whole device
|mtd_oobtest: written up to eraseblock 0
|mtd_oobtest: written 4 eraseblocks
|mtd_oobtest: verifying all eraseblocks
|mtd_oobtest: error @addr[0x0:0x19] 0x9a -> 0x78 diff 0xe2
|mtd_oobtest: error @addr[0x0:0x1a] 0xcc -> 0x0 diff 0xcc
|mtd_oobtest: error @addr[0x0:0x1b] 0xe0 -> 0x85 diff 0x65
|mtd_oobtest: error @addr[0x0:0x1c] 0x60 -> 0x62 diff 0x2
|mtd_oobtest: error @addr[0x0:0x1d] 0x69 -> 0x45 diff 0x2c
|mtd_oobtest: error @addr[0x0:0x1e] 0xcd -> 0xa0 diff 0x6d
|mtd_oobtest: error @addr[0x0:0x1f] 0xf2 -> 0x60 diff 0x92
|mtd_oobtest: error: verify failed at 0x0
[...]

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Fixes: a894cf6c5a82 ("mtd: nand: mxc: switch to mtd_ooblayout_ops")
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>