dt-bindings: phy: rockchip: Convert RK3399 PCIe PHY to schema

Convert the Rockchip RK3399 PCIe PHY to DT schema format. Move the
example to the GRF binding as that has the complete block.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20250415011824.2320039-1-robh@kernel.org


Signed-off-by: Vinod Koul <vkoul@kernel.org>