mtd: nand: denali: fix unaligned cache operations on ARMv7 SoCs

If the OOB size is not multiple of the cache line size, the ARMv7
cache operation still prints "Misaligned operation at range".

=> nand info

Device 0: nand0, sector size 256 KiB
  Page size       4096 b
  OOB size         224 b
  Erase size    262144 b
  subpagesize     4096 b
  options     0x00104200
  bbt options 0x00060000
=> nand dump 0
CACHE: Misaligned operation at range [9fb15280, 9fb16360]
CACHE: Misaligned operation at range [9fb15280, 9fb16360]
CACHE: Misaligned operation at range [9fb15280, 9fb16360]
CACHE: Misaligned operation at range [9fb15280, 9fb16360]
  ...

The cache flushing operations won't happen in this case to cover all of
the range to fix this by making sure we have things aligned.

Reported-by: Marek Vasut <marex@denx.de>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
[trini: Reword the commit message to be clear this is a direct problem
rather than just a warning]