net: sctp: remove cast for kmalloc/kzalloc return value

remove cast for kmalloc/kzalloc return value.

Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Cc: Vlad Yasevich <vyasevich@gmail.com>
Cc: Sridhar Samudrala <sri@us.ibm.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-sctp@vger.kernel.org
Signed-off-by: Jiri Kosina <jkosina@suse.cz>