lxfb: Maintain video processor palette through suspend/resume

The Geode X driver uses both of the LX's palettes, one for gamma
correction and one for colormaps.

The kernel driver currently only backs up the one used for colormaps
during suspend/resume. If you mess with gamma settings and do a
suspend/resume, colors go funny.

Fix this by backing up the video proc palette during suspend/resume,
alongside the display controller one which is already handled.

Signed-off-by: Daniel Drake <dsd@laptop.org>
Acked-by: Andres Salomon <dilinger@queued.net>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>