[U-Boot] Various clean-ups for a4m072 board support

[Ilya Yanok]

Hello,

these patches clean up the support for a4m072 board and related things.
Fourth patch is pretty generic actually but as it's only needed for
a4m072 AFAIK I post it in these series.

Patches:
[PATCH 1/5] a4m072: changes to the default environment
[PATCH 2/5] a4m072: change 'display' command implementation
[PATCH 3/5] led_display: remove unused DISPLAY_MARK define
[PATCH 4/5] cfi_flash: handle 'chip size exceeds address window' situation
[PATCH 5/5] a4m072: add CONFIG_SYS_FLASH_BANKS_SIZES define

Regards, Ilya.

Signed-off-by: Ilya Yanok <yanok at emcraft.com>