usb: dwc3: gadget: Clear ep descriptor last

Until the endpoint is disabled, its descriptors should remain valid.
When its requests are removed from ep disable, the request completion
routine may attempt to access the endpoint's descriptor. Don't clear the
descriptors before that.

Fixes: f09ddcfc

 ("usb: dwc3: gadget: Prevent EP queuing while stopping transfers")
Cc: stable@vger.kernel.org
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/45db7c83b209259115bf652af210f8b2b3b1a383.1668561364.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>