pmdomain: renesas: use menu for Renesas

Current Renesas PM Domains appears on top page. Let's create new
menu for Renesas.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/87jz4qcacr.wl-kuninori.morimoto.gx@renesas.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>