gma500: Add device framework

The devices have various internal differences so we have some abstractions
to hide the ugly differences and we then wrap them up in standard
interfaces. Add these bits

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --cc drivers/gpu/drm/gma500/backlight.c
Simple merge

diff --cc drivers/gpu/drm/gma500/power.c
Simple merge

diff --cc drivers/gpu/drm/gma500/power.h
Simple merge