[media] dib0700: do not lock interruptible on tear-down paths

When mutex_lock_interruptible is used on paths where a signal can be
pending, the device is not closed properly and cannot be reused.
This usually happens when you start tzap for example and send it a
TERM signal. The signal is pending while tear-down routines are
called. Hence streaming is not properly stopped in that case. And
the device stops working from that moment on.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/usb/dvb-usb/dib0700_core.c

@@ -561,10 +561,7 @@ int dib0700_streaming_ctrl(struct dvb_usb_adapter *adap, int onoff)
 		}
 	}
 
-	if (mutex_lock_interruptible(&adap->dev->usb_mutex) < 0) {
-		err("could not acquire lock");
-		return -EINTR;
-	}
+	mutex_lock(&adap->dev->usb_mutex);
 
 	st->buf[0] = REQUEST_ENABLE_VIDEO;
 	/* this bit gives a kind of command,