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

commit df86b576 upstream.

466e69b8 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>