Add the missing unlock before return from function xenhcd_urb_request_done()
and xenhcd_conn_notify() in the error handling case.

Fixes: 494ed399 ("usb: Introduce Xen pvUSB frontend (xen hcd)")
Reported-by: Hulk Robot <hulkci@huawei.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20211215035805.375244-1-yangyingliang@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>