sctp: reduce memory footprint of sctp_chunk structure

sctp_chunks should be put on a diet.  This is some of the low hanging
fruit that we can strip out.  Changes all the __s8/__u8 flags to
bitfields.  Saves 12 bytes per chunk.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
diff --git a/net/sctp/output.c b/net/sctp/output.c
index 225c712..c3f417f 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -699,7 +699,7 @@
 	 *    When a Fast Retransmit is being performed the sender SHOULD
 	 *    ignore the value of cwnd and SHOULD NOT delay retransmission.
 	 */
-	if (chunk->fast_retransmit <= 0)
+	if (chunk->fast_retransmit != SCTP_NEED_FRTX)
 		if (transport->flight_size >= transport->cwnd) {
 			retval = SCTP_XMIT_RWND_FULL;
 			goto finish;