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/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index d68869f..99fe074 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1211,7 +1211,7 @@
 	 */
 	retval->tsn_missing_report = 0;
 	retval->tsn_gap_acked = 0;
-	retval->fast_retransmit = 0;
+	retval->fast_retransmit = SCTP_CAN_FRTX;
 
 	/* If this is a fragmented message, track all fragments
 	 * of the message (for SEND_FAILED).