nir/validate: don't require offset src to be 0 if constant

nir_opt_constant_folding does the folding, so this can be non-zero before
that.

Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38277>

src/compiler/nir/nir_validate.c

@@ -857,7 +857,7 @@ validate_intrinsic_instr(nir_intrinsic_instr *instr, validate_state *state)
                             (state->shader->info.stage == MESA_SHADER_FRAGMENT &&
                              instr->intrinsic == nir_intrinsic_load_input_vertex));
 
-         /* Non-zero src offset with num_slots == 1 is disallowed. */
+         /* Non-constant src offset with num_slots == 1 is disallowed. */
          if (sem.num_slots == 1) {
             nir_src *offset_src = nir_get_io_offset_src(instr);
 
@@ -889,8 +889,7 @@ validate_intrinsic_instr(nir_intrinsic_instr *instr, validate_state *state)
              * So allow phis in offset_src with num_slots == 1 for now.
              */
             validate_assert(state,
-                            (nir_src_is_const(*offset_src) &&
-                             nir_src_as_uint(*offset_src) == 0) ||
+                            nir_src_is_const(*offset_src) ||
                             nir_def_is_phi(offset_src->ssa));
          }
       }