sctp: move up sctp_auth_init_hmacs() in sctp_endpoint_init()

sctp_auth_init_hmacs() is called only when ep->auth_enable is set.
It better to move up sctp_auth_init_hmacs() and remove auth_enable
check in it and check auth_enable only once in sctp_endpoint_init().

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>