drm/vc4: fix a bounds check

We accidentally return success even if vc4_full_res_bounds_check() fails.

Fixes: d5b1a78a

 ("drm/vc4: Add support for drawing 3D frames.")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Eric Anholt <eric@anholt.net>