Add support for iWave iW-RainboW-G23S single board computer based on
 RZ/G1C.
Signed-off-by: NBiju Das <biju.das@bp.renesas.com>
Reviewed-by: NFabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>