compositor: update scissor region before using it

Subsurfaces inherit the scissor region from the parent surface. Currently the region is updated at the end of weston_view_update_transform(). As a result, the old region is used to clip the transform.boundingbox of the subsurface.

Change the order to update the scissor region after the transform.matrix is updated but before it is used.

Signed-off-by: Michael Olbrich m.olbrich@pengutronix.de