omapfb: Add support for the Amstrad Delta LCD

This is an updated version of the LCD driver for the Amstrad Delta to
take into account the recent changes to the omapfb infrastructure. The
Delta features a 480x320 12 bit DSTN panel.

Signed-off-by: Jonathan McDowell <noodles@earth.li>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Imre Deak <imre.deak@nokia.com>