ARM: da850-evm: Unify config options with Kconfig

There are two options that are currently whitelisted, but they
are redundant, because there are not necessary since Kconfig options
exist to basically state the same thing.

CONFIG_DIRECT_NOR_BOOT and CONFIG_USE_NOR are both set together and
only used by the da850 when booting from NOR, however the only time
CONFIG_MTD_NOR_FLASH is configured is when booting from NOR. Since
NOR doesn't need SPL, the options for SPL can be moved to a check for
building SPL instead of checking for NOR.

This patch removes the checks for these two config options and unifies
the checks around the Kconfig option of CONFIG_MTD_NOR_FLASH.

Since this board is the only board that uses these two config options,
they can be removed from the whitelist table.

Signed-off-by: Adam Ford <aford173@gmail.com>