usb: dwc3: gadget: move requests to cancelled_list

commit d4f1afe5e896c18ae01099a85dab5e1a198bd2a8 upstream

Whenever we have a request in flight, we can move it to the cancelled
list and later simply iterate over that list and skip over any TRBs we
find.

Cc: Fei Yang <fei.yang@intel.com>
Cc: Sam Protsenko <semen.protsenko@linaro.org>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: linux-usb@vger.kernel.org
Cc: stable@vger.kernel.org # 4.19.y
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
(cherry picked from commit d4f1afe5e896c18ae01099a85dab5e1a198bd2a8)
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>