usb: dwc3: gadget: Set IOC if not enough for extra TRBs

If we run out of TRBs because we need extra TRBs, make sure to set the
IOC bit for the previously prepared TRB to get completion notification
to free up TRBs to resume later.

Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>