ipip: add module alias for tunl0 tunnel device

If ipip is built as a module the 'ip tunnel add' command would fail because
the ipip module was not being autoloaded.  Adding an alias for
the tunl0 device name cause dev_load() to autoload it when needed.
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ipip.c

@@ -913,3 +913,4 @@ static void __exit ipip_fini(void)
 module_init(ipip_init);
 module_exit(ipip_fini);
 MODULE_LICENSE("GPL");
+MODULE_ALIAS("tunl0");