drm/omap: Enable DT support for DMM

Enable use of DT for DMM/Tiler.

Originally worked on by Andy Gross <andygro@gmail.com>

Cc: Andy Gross <andygro@gmail.com>
Cc: DRI Development <dri-devel@lists.freedesktop.org>
Signed-off-by: Archit Taneja <archit@ti.com>
[tomi.valkeinen@ti.com: use of_match_ptr()]
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>