Restore the status of ep->stopped in function net2272_dequeue().

When the given request is not found in the endpoint queue
the function returns -EINVAL without restoring the state of
ep->stopped. Thus the endpoint keeps blocked and does not transfer
any data anymore.

This fix is only compile-tested, since we do not have a
corresponding hardware. An analogous fix was tested in the sibling
driver. See "usb: gadget: net2280: Fix net2280_dequeue()"
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Guido Kiener <guido.kiener@rohde-schwarz.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>