usb: dwc3: Set default mode for DWC_usb3 v3.30a and higher

DWC_usb31 and DWC_usb3 v3.30a and higher do not support OTG mode. If
the controller supports DRD but the dr_mode is not specified or set to
OTG, then set the mode to peripheral.

Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>