st/mesa: set result writemask based on ir type

This prevents textureQueryLevels, which maps as LODQ, from ending up
with a xyzw writemask, which is illegal.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100061
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
(cherry picked from commit dab88e9af7a35ebcdd0fc87df97f4b13e908552a)
1 file changed