pan/bi: Fix 1D array indexing on Valhall

pan/bi: Fix 1D array indexing on Valhall

Array index always goes in the fourth 16-bit component on Valhall. I'm unsure
whether that should also apply to Bifrost. f256ec2a881 ("pan/bi: Fix 1DArray
image coordinate retrieval") says that it should be in the third component on
Bifrost, but I can't remember why that would be the case.

Fixes OpenCL test image_streams.write.1darray on Valhall.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18656>