sctp: change auth event type name to SCTP_AUTHENTICATION_EVENT

This patch change the auth event type name to SCTP_AUTHENTICATION_EVENT,
which is based on API extension compliance.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>