amd/llvm: Mark pointer function arguments as 32-byte aligned.

amd/llvm: Mark pointer function arguments as 32-byte aligned.

Otherwise LLVM does not see the pointers as allowing speculative
loads.

The pipeline-db results are pretty wild, but mostly what is to be
expected from allowing more code movement in LLVM:

Totals from affected shaders:
SGPRS: 157728 -> 168336 (6.73 %)
VGPRS: 158628 -> 158664 (0.02 %)
Spilled SGPRs: 10845 -> 24753 (128.24 %)
Spilled VGPRs: 13 -> 13 (0.00 %)
Private memory VGPRs: 0 -> 0 (0.00 %)
Scratch size: 8 -> 8 (0.00 %) dwords per thread
Code Size: 17189180 -> 17313712 (0.72 %) bytes
LDS: 204 -> 204 (0.00 %) blocks
Max Waves: 5700 -> 5687 (-0.23 %)
Wait states: 0 -> 0 (0.00 %)

This gives some boosts for shaders we can move a descriptor load
outside a loop.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3159>