[SCTP]: make 2 functions static

This patch makes the following needlessly global functions static:
- ipv6.c: sctp_inet6addr_event()
- protocol.c: sctp_inetaddr_event()

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>