nand: fix buffer alignment in new verification feature

nand: fix buffer alignment in new verification feature

On systems with caches enabled, NAND I/O may need to flush/invalidate
the cache during read/write operations. For this to work correctly, all
buffers must be cache-aligned. Fix nand_verify*() to allocate aligned
buffers.

This prevents cache alignment warnings from being spewed when using
U-Boot to write an updated version of itself to flash on NVIDIA Tegra
Seaboard (after perturbation of stack/data layout in current
u-boot-dm/next branch).

I have validatd (executed) nand_verify(), but I don't think I've executed
nand_verify_page_oob(); testing of that would be useful.

Cc: Peter Tyser <ptyser@xes-inc.com>
Cc: Heiko Schocher <hs@denx.de>
Cc: Scott Wood <scottwood@freescale.com>
Fixes: 59b5a2ad83df ("nand: Add verification functions")
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Scott Wood <scottwood@freescale.com>