drm/savage: re-add busmaster enable, regression fix

commit df86b5765a48d5f557489577652bd6df145b0e1b upstream.

466e69b8b03b8c1987367912782bc12988ad8794 dropped busmaster enable from the
global drm code and moved it to the individual drivers, but missed the savage
driver. So, this re-adds busmaster enable to the savage driver, fixing the
regression.

Signed-off-by: Florian Zumbiehl <florz@florz.de>
Reviewed-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>