a4m072: add CONFIG_SYS_FLASH_BANKS_SIZES define

This patch adds CONFIG_SYS_FLASH_BANKS_SIZES define to make use of new
cfi_flash driver ability to detect flash chips that are bigger than a
corresponding address window (we have such situation on some revs of
a4m072).

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