net: sctp: remove unused multiple cookie keys

Vlad says: The whole multiple cookie keys code is completely unused
and has been all this time. Noone uses anything other then the
secret_key[0] since there is no changeover support anywhere.

Thus, for now clean up its left-over fragments.

Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Vlad Yasevich <vyasevic@redhat.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index fdeb85a..0e0f9d2 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -1236,10 +1236,7 @@
 	 *	      Discussion in [RFC1750] can be helpful in
 	 *	      selection of the key.
 	 */
-	__u8 secret_key[SCTP_HOW_MANY_SECRETS][SCTP_SECRET_SIZE];
-	int current_key;
-	int last_key;
-	int key_changed_at;
+	__u8 secret_key[SCTP_SECRET_SIZE];
 
  	/* digest:  This is a digest of the sctp cookie.  This field is
  	 * 	    only used on the receive path when we try to validate