sctp: remove the else path

Make the code more simplification.

Acked-by: Neil Horman <nhorman@tuxdriver.com>
Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Wang Weidong <wangweidong1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>