nir/opt_intrinsics: Report progress for the gl_SampleMask optimization

Fixes: d3ce8a7f6b "nir: optimize gl_SampleMaskIn to gl_HelperInvocation..."
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7366>

src/compiler/nir/nir_opt_intrinsics.c

@@ -86,6 +86,7 @@ opt_intrinsics_impl(nir_function_impl *impl,
                      nir_ssa_def_rewrite_uses(&alu->dest.dest.ssa,
                                               nir_src_for_ssa(new_expr));
                      nir_instr_remove(&alu->instr);
+                     progress = true;
                      continue;
                   }
                }