ARM: dts: sun8i: Add leds and switch on Orangepi Plus boards

OrangePi Plus board has dwo leds - green ("pwr") and red ("status")
and a switch ("sw4"). This patch describes them in a devicetree.

Signed-off-by: Krzysztof Adamski <k@japko.eu>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>