commit 855f5f1d upstream.

We were using the wrong set_properly callback so we always
ended up with Full scaling even if something else (Center or
Full aspect) was selected.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>