If gre is built as a module the 'ip tunnel add' command would fail because
the ip_gre module was not being autoloaded. Adding an alias for
the gre0 device name cause dev_load() to autoload it when needed.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Signed-off-by: David S. Miller <davem@davemloft.net>