Fix the following issues with the gpio_keys node:
1) Use of undocumented input-name property
2) Use of a unit-address on the sw2 node
3) Having "PL03" in the pinctrl node which does not exist, this should
   be "PL3"

And add support for the sw2 button on the board.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>