phy: rockchip: Add Rockchip Synopsys PCIe 3.0 PHY

Add the Rockchip Synopsys based PCIe 3.0 PHY driver as
part of Generic PHY framework.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Kever <Yang&lt;kever.yang@rock-chips.com>