drm/omap: fix plane rotation

Plane rotation with omapdrm is currently broken.
It seems omap_plane_mode_set() expects width and height in screen
coordinates, so pass it like that.

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>