usb: dwc3: gadget: Give back staled requests

If a request is dequeued, the transfer is cancelled. Give back all
the started requests.

In most scenarios, the function driver dequeues all requests of a
transfer when there's a failure. If the function driver follows this,
then it's fine. If not, then we'd be skipping TRBs at different points
within the dequeue and enqueue pointers, making dequeue/enqueue pointers
useless. To enforce and make sure that we're properly skipping TRBs,
cancel all the started requests and give back all the cancelled requests
to the function drivers.

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