CRIS: stop checking for MTD_CONCAT

CRIS: stop checking for MTD_CONCAT

As MTD_CONCAT support is becoming an integral part of MTD core,
there is no need for it's special treatment. So stop checking for
MTD_CONCAT availability.

Acked by Jesper Nilsson <[email protected]> for merging this
via the MTD tree.

Signed-off-by: Dmitry Eremin-Solenikov <[email protected]>
Acked-by: Stefan Roese <[email protected]>
Signed-off-by: Jesper Nilsson <[email protected]>
Signed-off-by: Artem Bityutskiy <[email protected]>
Signed-off-by: David Woodhouse <[email protected]>