The USB 3.0 PHY modules of R-Car Gen3 SoCs have:
 - Spread spectrum clock (ssc).
 - Using USB 2.0 EXTAL clock instead of USB 3.0 clock.
 - Enabling VBUS detection for usb3.0 peripheral.

So, this driver supports these features.
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>