This patch is to remove the typedef sctp_datahdr_t, and replace with
struct sctp_datahdr in the places where it's using this typedef.

It is also to use izeof(variable) instead of sizeof(type).
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>