nir/lower_robust_access: handle MSAA images

We need to check the sample too. fixes on Honeykrisp with MSAA storage images:

dEQP-VK.robustness.robustness2.bind.notemplate.r32i.dontunroll.nonvolatile.storage_image.fmt_qual.img.samples_4.2d_array.comp

cc @itoral