radv: Deal with derefs from opaque types in function parameters.

radv: Deal with derefs from opaque types in function parameters.

Needs more copy propagation before nir_opt_derefs picks it up.

Note that the full general problem of opaque types stored in
intermediate variables is still open, but that seems like a whole
can of worms, and no sense to have gfxbench stay broken during the
time it takes to solve that.

Cc: mesa-stable
Gitlab: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5945
Reviewed-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17012>