usb-linux: Don't try to open the same device twice

If a user wants to redirect 2 identical usb sticks, in theory this is
possible by doing:
usb_add host:1234:5678
usb_add host:1234:5678

But this will lead to us trying to open the first stick twice, since we
don't break the loop after having found a match in our filter list, so the next'
filter list entry will result in us trying to open the same device again.

Fix this by adding the missing break.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

usb-linux.c

@@ -1671,6 +1671,7 @@ static int usb_host_auto_scan(void *opaque, int bus_num, int addr, char *port,
         DPRINTF("husb: auto open: bus_num %d addr %d\n", bus_num, addr);
 
         usb_host_open(s, bus_num, addr, port, product_name, speed);
+        break;
     }
 
     return 0;