usb: dwc3: add hsphy_interface property

Platforms that have configured DWC_USB3_HSPHY_INTERFACE with
value 3, i.e. UTMI+ and ULPI, need to inform the driver of
the actual HSPHY interface type with the property. "utmi" if
the interface is UTMI+ or "ulpi" if the interface is ULPI.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-by: David Cohen <david.a.cohen@linux.intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>