usb: dwc3: ULPI or UTMI+ select

Make selection between ULPI and UTMI+ interfaces possible by
providing definition for the bit in Global USB2 PHY
Configuration Register that controls it.

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>