pinctrl: sh-pfc: r8a7791 PFC support

Add PFC support for the r8a7791 SoC V2 including pin groups for
on-chip devices such as MSIOF, SCIF, USB, MMC, SDHI, DU.

Signed-off-by: Hisashi Nakamura <hisashi.nakamura.ak@renesas.com>
Signed-off-by: Kunihito Higashiyama <kunihito.higashiyama.ur@renesas.com>
Signed-off-by: Yoshikazu Fujikawa <yoshikazu.fujikawa.ue@renesas.com>
Signed-off-by: Nobuyuki HIRAI <nobuyuki.hirai.xe@renesas.com>
Signed-off-by: Shinobu Uehara <shinobu.uehara.xc@renesas.com>
Signed-off-by: Koji Matsuoka <koji.matsuoka.xm@renesas.com>
Signed-off-by: Ryo Kataoka <ryo.kataoka.wt@renesas.com>
[damm@opensource.se: Forward ported to upstream, minor fixes]
Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>