Add support for input switch SW3 on the Renesas RZ/A2M EVB
development board.

Note that this uses the IRQ interrupt, as the RZ/A2 GPIO controller
does not include interrupt support
Signed-off-by: NChris Brandt <chris.brandt@renesas.com>
Reviewed-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>