gma500: begin adding CDV specific code

A lot of the intel_display stuff is duplicated, but we will add it first,
clean it up and then investigate the best way to merge stuff.

This first block integrates the various basic chunks of the CDV display setup.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>