drm/mgag200: Fix framebuffer base address programming

drm/mgag200: Fix framebuffer base address programming

commit 9f1d036648c1c5ed81b0e98d7a06d55df972701e upstream.

Higher bits of the base address of framebuffers weren't being
programmed properly. This caused framebuffers that didn't happen to be
allocated at a low enough address to not be displayed properly.

Signed-off-by: Christopher Harvey <charvey@matrox.com>
Signed-off-by: Mathieu Larouche <mathieu.larouche@matrox.com>
Acked-by: Julia Lemire <jlemire@matrox.com>
Tested-by: Julia Lemire <jlemire@matrox.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>