nir: handle frag_coord_z/w intrinsics

so we can gather_info later.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Mary Guillemard <mary.guillemard@collabora.com>
Reviewed-by: Marek Olšák <maraeo@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36265>

src/compiler/nir/nir.c

@@ -2455,6 +2455,8 @@ nir_system_value_from_intrinsic(nir_intrinsic_op intrin)
    case nir_intrinsic_load_invocation_id:
       return SYSTEM_VALUE_INVOCATION_ID;
    case nir_intrinsic_load_frag_coord:
+   case nir_intrinsic_load_frag_coord_z:
+   case nir_intrinsic_load_frag_coord_w:
       return SYSTEM_VALUE_FRAG_COORD;
    case nir_intrinsic_load_pixel_coord:
       return SYSTEM_VALUE_PIXEL_COORD;