If present, honor the USB port mode (host or peripheral) set on DTS, if not,
keep the beaglebone defaults: USB0 -> peripheral/gadget, USB1 -> host.

This is only a workaround as in fact fact this hardware is capable of detect
the USB port mode based on type of cable and act according with the detected
mode. Unfortunately the driver does not handle that at moment.

MFC after: 3 days
Sponsored by: Rubicon Communications, LLC (Netgate)