OXNAS: clean up unused env variable
OXNAS: adjust nand env layout

Move the environment to leave extra room for u-boot image.
And the redundant copy of env is removed.
cmd_ide: reduce size in SPL build
OXNAS: SPL: reduce SPL code size

Seems SPL size has a limit of 32K bytes even though SRAM has 64KiB.
fs/ext4: fix filename buffer initialization

Quoted from ALLOC_CACHE_ALIGN_BUFFER's comment:
The buffer variable created by the macro is a pointer to the specified
type, and NOT an array of the specified type.

Signed-off-by: Ma Haijun <mahaijuns@gmail.com>