OMAPDSS: RFBI: Remove partial update support

Partial update suppport was removed from DISPC and DSI sometime back. The RFBI
driver still tries to support partial update without the underlying support in
DISPC.

Remove partial update support from RFBI, only support updates which span acros
the whole panel size. This also helps in DSI and RFBI having similar update
ops.

Signed-off-by: Archit Taneja <archit@ti.com>