Revert "sctp: fix call to SCTP_CMD_PROCESS_SACK in sctp_cmd_interpreter()"

This reverts commit de77b795, which was
commit f6e80abe upstream.

This fix was only appropriate for Linux 3.7 onward, and introduced a
regression when applied to earlier versions.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

net/sctp/sm_sideeffect.c

@@ -1604,9 +1604,8 @@ static int sctp_cmd_interpreter(sctp_event_t event_type,
 					asoc->outqueue.outstanding_bytes;
 			sackh.num_gap_ack_blocks = 0;
 			sackh.num_dup_tsns = 0;
-			chunk->subh.sack_hdr = &sackh;
 			sctp_add_cmd_sf(commands, SCTP_CMD_PROCESS_SACK,
-					SCTP_CHUNK(chunk));
+					SCTP_SACKH(&sackh));
 			break;
 
 		case SCTP_CMD_DISCARD_PACKET: