ARM: dts: rockchip: fix adc-keys sub node names

Fix adc-keys sub node names on Rockchip boards,
so that they match with regex: '^button-'

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/7a0013b1-3a55-a344-e9ea-eacb4b49433c@gmail.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>