omapfb: Fix 12-bit display (RGB444 color mode) handling

omapfb: Fix 12-bit display (RGB444 color mode) handling

Support for RGB444 (12-bit) pixel format has been introduced into omapfb/lcdc
by Mark Underwood on 2006-05-26 (commit
f74edb6668aad9fc8e81585861b18f996c78a574) in preparation for Amstrad Delta
(E3) videophone LCD display support.

Before the Amstrad Delta LCD patch by Jonathan McDowell was applied (on
2006-08-04, commit 8d22fb2ea004cdb6379b54c1a8fd1546cfe40ed7), omapfb and lcdc
code was changed substantially (commit
e563dc81aa01bd8bbb01bc53975a15c398715f62 dated 2006-06-26) in a way that broke
Mark's 12-bit display support. Than, a patch by Jonathan, that supposed to
correct the problem, was introduced immediatelly (on 2006-08-04, commit
e10a75b49e7a57ae17c28b705153c70eba15a8ef).

As a result, the Amstrad Delta display was working correctly at boot time,
with fbset reporting:

	geometry 480 320 480 320 16
	...
	rgba 4/8,4/4,4/0,0/0

However, after first framebuffer reinitialization, colors were no longer being
displayed correctly and fbset was reporting:

        rgba 5/11,6/5,5/0,0/0

The patch tries to correct the issue by setting plane->color_mode depending on
panel->bpp, not var->bits_per_pixel.

Created and tested on Amstrad Delta against linux-2.6.33-rc3.

Signed-off-by: Janusz Krzysztofik <jkrzysz@tis.icnet.pl>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>