rockchip: puma-rk3399: add button support

The Haikou Devkit exposes 4 buttons over GPIO so let's enable their
support so their status can be queried from the `button` command from
the CLI.

Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
1 file changed