usb: dwc3: Add boundary check while traversing the TRB ring buffer

During the dequeue operation of an usb request we traverse through the
TRBs and reset the HWO bit. Without a boundary check we might iterate
past the TRB ring which results in a page fault. Fix this by adding a
link TRB boundary check while traversing the ring buffer.

Change-Id: I7ae63ed7cc829a8105f2e81b12216af910aa253a
Signed-off-by: Elson Roy Serrao <eserrao@codeaurora.org>