Add the documentation for the rk3568-usb2phy-grf node, which is separate from the usb2phy node on this chip. Signed-off-by: Peter Geis <pgwipeout@gmail.com> Acked-by: Rob Herring <robh@kernel.org> Link: https://lore.kernel.org/r/20211215210252.120923-2-pgwipeout@gmail.com Signed-off-by: Heiko Stuebner <heiko@sntech.de>