ARM: dts: pcduino: Enable user LED and button support for pcDuino

The pcDuino board has LEDs connected to PH15/PH16, and back/home/menu
buttons to PH17/18/19 respectively. Enable these via gpio-leds and
gpio-keys. This is shared across the v1 and v2 versions of the board.

Tested on a v2 and verified against the schematics of a v1.

Signed-off-by: Zoltan HERPAI <wigyori@uid0.hu>
Acked-by: Hans de Goede <hdegoede@redhat.com>
[Maxime: Added some newlines between the button nodes]
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>