Use the new display drivers for RX51 board.

The new OMAP display drivers were merged for 3.11, and we can now change
the board files to use the new ones and phase out the old ones.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>
Tested-by: NAaro Koskinen <aaro.koskinen@iki.fi>
Acked-by: NTony Lindgren <tony@atomide.com>