nir: fix lower_non_uniform_access pass

Obviously missing the instruction insertion into the SSA list.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: 3bd5457641 ("nir: Add a lowering pass for non-uniform resource access")
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compiler/nir/nir_lower_non_uniform_access.c

@@ -34,6 +34,7 @@ read_first_invocation(nir_builder *b, nir_ssa_def *x)
    first->src[0] = nir_src_for_ssa(x);
    nir_ssa_dest_init(&first->instr, &first->dest,
                      x->num_components, x->bit_size, NULL);
+   nir_builder_instr_insert(b, &first->instr);
    return &first->dest.ssa;
 }