arm64: dts: renesas: r8a77995: draak: Add SW56 support

Add support for SW56 via "gpio-keys" on the R-Car D3 Draak board.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Link: https://lore.kernel.org/r/162416648156.11444.10425966868846910243.sendpatchset@octo


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>