pinctrl: add a pincontrol driver for BCM63268

pinctrl: add a pincontrol driver for BCM63268

Add a pincontrol driver for BCM63268. BCM63268 allows muxing GPIOs
to different functions. Depending on the mux, these are either single
pin configurations or whole pin groups.

Co-developed-by: Jonas Gorski <jonas.gorski@gmail.com>
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Link: https://lore.kernel.org/r/20210324081923.20379-20-noltari@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>