ARM: OMAP: Add external LCD controller support for DSP Gateway

If an external LCD controller is in manual update mode, the DSP
must let the FB driver know when a frame should be send over the
remote framebuffer interface.

Original code by Toshihiro, FB parts by Imre.

Signed-off-by: Imre Deak <imre.deak@nokia.com>
Signed-off-by: Juha Yrjölä <juha.yrjola@nokia.com>