v3d: fix checking twice auf flag

Seems a C&P error, and should check for auf/muf.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110902


Fixes: 8f065596 "v3d: Add an optimization pass for redundant flags updates."

Reviewed-by: Eric Anholt <eric@anholt.net>
(cherry picked from commit 17c2c9cd)