ARM: shmobile: Let KZM9D multiplatform boot with KZM9D DTB

Let the multiplatform KZM9D support boot with the
legacy DTS for KZM9D as well as the KZM9D reference DTS.

Signed-off-by: Magnus Damm <damm@opensource.se>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>