usb: phy: Add RCAR Gen2 USB phy

This adds RCAR Gen2 USB phy support. The driver configures
USB channels 0/2 which are shared between PCI USB hosts and
USBHS/USBSS devices. It also controls internal USBHS phy.

Signed-off-by: Valentine Barshak <valentine.barshak@cogentembedded.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>