ac/llvm: fix invalid IR if image stores are shrinked using the format

It's not always v4f32 (or v4f16 for 16-bit) when image stores are
shrinked using the format.

This fixes a ton of crashes with RADV_DEBUG=checkir,llvm.

Fixes: e4d75c22beb ("nir/opt_shrink_vectors: shrink image stores using the format")
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6882>
1 file changed