Now that we're using load/store_reg intrinsics, the previous checks for
registers aren't what we want. Instead, we need to be looking for a mov
or vec where both the destination and a source are load/store_reg with
matching decl_reg.
Fixes: b8209d69ff ("intel/fs: Add support for new-style registers")
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24310>
965bbe5286