sctp: remove the typedef sctp_cwr_chunk_t

Remove this typedef including the struct, there is even no places
using it.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/sctp.h

@@ -535,11 +535,6 @@ struct sctp_cwrhdr {
 	__be32 lowest_tsn;
 };
 
-typedef struct sctp_cwr_chunk {
-	struct sctp_chunkhdr chunk_hdr;
-	struct sctp_cwrhdr cwr_hdr;
-} sctp_cwr_chunk_t;
-
 /* PR-SCTP
  * 3.2 Forward Cumulative TSN Chunk Definition (FORWARD TSN)
  *