gpio: renesas: Migrate to pinctrl GPIO accessors

gpio: renesas: Migrate to pinctrl GPIO accessors

Switch to generic pin controller API for configuring pins as GPIOs
instead of using the ad-hoc call into the R-Car PFC driver. Moreover,
add .free() implementation for the GPIO controller.

Signed-off-by: Marek Vasut <[email protected]>
Cc: Alex Kiernan <[email protected]>
Cc: Christoph Muellner <[email protected]>
Cc: Eugeniu Rosca <[email protected]>
Cc: Patrice Chotard <[email protected]>
Cc: Patrick DELAUNAY <[email protected]>
Cc: Philipp Tomsich <[email protected]>
Cc: Simon Glass <[email protected]>