drm/gma500: Add support for rebuilding the gtt

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
drm/gma500: Activate the gtt rebuild on suspend/resume

This patch activates the rebuilding of the gtt. Currently we reinitialize the
gtt by inserting the stolen pages again and map the rest to our scratch page.
Then we go about restoring the needed ranges. This is a bit overkill but right
now we don't have that much to restore so better safe than sorry.

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
drm/gma500: Add hooks for hibernation

Currently we do whatever is done during suspend/resume but we might need some
more work for hibernation so keep them in separate functions.

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
drm/gma500: Fix hibernation problems on sdvo encoders

The state of the SDVO chip is more difficult to save than the LVDS so we do a
full mode set on the crtc to get SDVO operational again. The SDVOB/C register is
also stored just in case we have special bits set in the future.

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>