sctp: fix a type cast warnings that causes a_rwnd gets the wrong value

These warnings were found by running 'make C=2 M=net/sctp/'.

Commit d4d6fb5787a6 ("sctp: Try not to change a_rwnd when faking a
SACK from SHUTDOWN.") expected to use the peers old rwnd and add
our flight size to the a_rwnd. But with the wrong Endian, it may
not work as well as expected.

So fix it by converting to the right value.

Fixes: d4d6fb5787a6 ("sctp: Try not to change a_rwnd when faking a SACK from SHUTDOWN.")
Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/sm_sideeffect.c

@@ -1680,8 +1680,8 @@ static int sctp_cmd_interpreter(enum sctp_event event_type,
 		case SCTP_CMD_PROCESS_CTSN:
 			/* Dummy up a SACK for processing. */
 			sackh.cum_tsn_ack = cmd->obj.be32;
-			sackh.a_rwnd = asoc->peer.rwnd +
-					asoc->outqueue.outstanding_bytes;
+			sackh.a_rwnd = htonl(asoc->peer.rwnd +
+					     asoc->outqueue.outstanding_bytes);
 			sackh.num_gap_ack_blocks = 0;
 			sackh.num_dup_tsns = 0;
 			chunk->subh.sack_hdr = &sackh;