phy: Add USB Type-C PHY driver for rk3399

Add a PHY provider driver for the rk3399 SoC Type-c PHY. The USB
Type-C PHY is designed to support the USB3 and DP applications.
The USB3 operates in SuperSpeed mode and the DP can operate at RBR,
HBR and HBR2 data rates. This driver create 2 PHY devices separately
for USB3 and DisplyPort, and registers them under the child node.

Signed-off-by: Chris Zhong <zyw@rock-chips.com>
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Tested-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>