nir/lower_non_uniform: improve code with the same texture and sampler indices
NIR can't CSE the read_first_invocation intrinsics, so we can end up creating iand(read_first_invocation(a) == a, read_first_invocation(a) == a)
NIR can't CSE the read_first_invocation intrinsics, so we can end up creating iand(read_first_invocation(a) == a, read_first_invocation(a) == a)