ac/nir: handle non-const offset with txf/txf_ms

It might be a vec2. If it's a constant, LLVM will fold it.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7077>
1 file changed