usb: dwc3: gadget: Properly handle ClearFeature(halt)

DWC3 must not issue CLEAR_STALL command to control endpoints. The
controller automatically clears the STALL when it receives the SETUP
token. Also, when the driver receives ClearFeature(halt_ep), DWC3 must
stop any active transfer from the endpoint and give back all the
requests to the function drivers.

Fixes: 72246da4 ("usb: Introduce DesignWare USB3 DRD Driver")
Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>