phy: usb: Add support for new Synopsys USB controller on the 7211b0

The 7211b0 has added the STB XHCI Synopsys controller and it
will be used instead of the RPi based DWC USB controller. The new
Synopsys XHCI controller core is the same one that is used on the
7216, but because of the way the STB USB PHY is used on both the A0
and B0, some of the PHY control is different.

Signed-off-by: Al Cooper <alcooperx@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>