mesa/st: only convert AND(a, NOT(b)) into MAD when not using native integers

mesa/st: only convert AND(a, NOT(b)) into MAD when not using native integers

Native integers imply a somewhat different handling of booleans. Instead
of being 1.0/0.0 floats, they are 0 (true) / -1 (false) integers. As such
the original optimization no longer applies.

Reported-by: Glenn Kennard <glenn.kennard@gmail.com>
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Cc: "10.2" <mesa-stable@lists.freedesktop.org>