davinci: omapl138_lcdk: use correct name for CONFIG_SYS_NAND_MASK_ALE

CONFIG_SYS_ALE_MASK is not used anywhere. It has probably been
renamed to CONFIG_SYS_NAND_MASK_ALE. Rename it and remove the former
from the config_whitelist.txt file.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Reviewed-by: Tom Rini <trini@konsulko.com>