usb: dwc2: gadget: stop current transfer on dequeue

If the request being dequeued is already started, disable endpoint
to stop the transfer and then call dwc2_hsotg_complete_request().
Endpoint will be re-enabled on next call to dwc2_hsotg_start_req().

Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@intel.com>
Tested-by: Robert Baldyga <r.baldyga@samsung.com>
Tested-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Tested-by: John Youn <johnyoun@synopsys.com>
Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>