dt-bindings: phy: rockchip: Add Naneng combo PHY bindings

Add the compatible strings for the Naneng combo PHY found on rockchip SoC.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Yifeng Zhao <yifeng.zhao@rock-chips.com>
Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Tested-by: Frank Wunderlich <frank-w@public-files.de>
Link: https://lore.kernel.org/r/20220208091326.12495-3-yifeng.zhao@rock-chips.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>