connector: add module alias

Since connector can be built as a module and uses netlink socket
to communicate. The module should have an alias to autoload when socket
of NETLINK_CONNECTOR type is requested.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: David S. Miller <davem@davemloft.net>