usbip: vhci_hcd: only return urb at enqueue when served

We handle USB_REQ_SET_ADDRESS at enqueue, so we want to perform
cleanup and giveback the urb. We should not call usb_hcd_giveback_urb
when we're cleaning up after a failed enqueue, though.

Only giveback the urb at cleanup when we claim to have served it.

Signed-off-by: Igor Kotrasinski <i.kotrasinsk@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>