ac/nir: fix out-of-bound access when loading constants from global

Global load/store instructions can't know if the offset is
out-of-bound because they don't use descriptors (no range).

Fix this by clamping the offset for arrays that are indexed
with a non-constant offset that's greater or equal to the array
size.

This fixes VM faults and GPU hangs with Dead Rising 4.

Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/2148


Fixes: 71a67942 ("ac/nir: Enable nir_opt_large_constants")
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
(cherry picked from commit a0f1a5fa)