gma500: 2D acceleration tidying

We have a FIXME to do the power management for which the framework now
exists, and we also need to deal with an erratum. Some operations exactly 8
pixels wide or high fail. The work around is to do two smaller ones (see
the Intel released X driver bits) but for console quite frankly if it's
8bits wide and/or high its not worth it so fall back.

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