ARM: shmobile: marzen: Remove DU platform device

Platform data support has been removed from the DU driver, drop DU
support from the legacy Marzen board file. The multiplatform DT-based
Marzen support should be used instead.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Dave Airlie <airlied@redhat.com>