gm107/ir: AL2P writes to a predicate register

gm107/ir: AL2P writes to a predicate register

We have to force it to write to predicate 7 (aka PT) in order for it not
to mess up another predicate. Unclear what would be returned in the
predicate, perhaps an error code for out-of-bounds requests. Blob
doesn't seem to check it.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Cc: mesa-stable@lists.freedesktop.org