Add device tree bindings for the gpio/pin/mux controller that is part of
the RP1 multi function device, and relative entries in MAINTAINERS file.
Signed-off-by: Andrea della Porta <andrea.porta@xxxxxxxx>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>