usb: dwc2: Fix dead code in hcd.c

Because usb_pipetype() masks urb->pipe, the default case can never be
hit. Remove it. This cleans up a coverity warning.

Signed-off-by: Vardan Mikayelyan <mvardan@synopsys.com>
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>