usb: dwc3: gadget: remove wait_end_transfer

commit fec9095bdef4e7c988adb603d0d4f92ee735d4a1 upstream

Now that we have a list of cancelled requests, we can skip over TRBs
when END_TRANSFER command completes.

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 fec9095bdef4e7c988adb603d0d4f92ee735d4a1)
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>