gma500: 2D polish

Tidy up the 2D bits. For the fill case the CPU seems to be able to
outperform the graphics engine for the cases we get, so don't bother
fixing it but throw it out.

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