gma500: Add the glue to the various BIOS and firmware interfaces

Some of this should one day become a library shared by i915 and gma500 I
suspct. Best however to deal with that later once it is all nice and
stably merged.

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