pinctrl: rmobile: Add Renesas RCar pincontrol driver

pinctrl: rmobile: Add Renesas RCar pincontrol driver

Add PFC pincontrol driver for the Renesas RCar Gen3 R8A7795 and R8A7796
SoCs. This driver uses the PFC pin tables from Linux, thus letting us
share the occassional fixes to those tables. This driver also has a DT
support, so the pinmux is configured from DT instead of the ad-hoc setup
in board file.

This driver is meant to replace the pinmux part of SH_GPIO_PFC driver.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>