OMAPDSS: DISPC/RFBI: Use dispc_mgr_set_lcd_timings() for setting lcd size

The RFBI driver uses dispc_mgr_set_lcd_size() to set the width and height of
the LCD manager. Replace this to use dispc_mgr_set_lcd_timings(), pass dummy
blanking parameters like done in the DSI driver.

This prevents the need to export dispc_mgr_set_lcd_size(), and use a common
function to set lcd timings.

Signed-off-by: Archit Taneja <archit@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>