dt-bindings: rockchip: Add BananaPi R2 Pro Board

Add Devicetree Binding for Bananapi R2 Pro Board based on rk3568 SoC

Co-developed-by: Peter Geis <pgwipeout@gmail.com>
Signed-off-by: Peter Geis <pgwipeout@gmail.com>
Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220123135116.136846-2-linux@fw-web.de
Signed-off-by: Heiko Stuebner <heiko@sntech.de>