freedreno/ir3: don't pass consts to madsh.m16 in MOD logic

madsh.m16 can't handle a const in src1, make sure to unconst it

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Cc: "10.3 10.4" <mesa-stable@lists.freedesktop.org>