sctp: remove the duplicate initialize

kzalloc had initialize the allocated memroy. Therefore, remove the
initialize with 0 and the memset.

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