[DCCP]: Adds the tx buffer sysctls

This one got lost on the way from Ian to Gerrit to me, fix it.

Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt
index 1910d09..dda1588 100644
--- a/Documentation/networking/dccp.txt
+++ b/Documentation/networking/dccp.txt
@@ -100,6 +100,10 @@
 seq_window = 100
 	The initial sequence window (sec. 7.5.2).
 
+tx_qlen = 5
+	The size of the transmit buffer in packets. A value of 0 corresponds
+	to an unbounded transmit buffer.
+
 Notes
 =====