[DCCP]: Fix comment about control sockets.

These sockets now have a bit other names and are no longer global.

Shame on me, I haven't provided a good comment for this when
sending DCCP netnsization patches.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index baa268d..b348dd7 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -32,7 +32,7 @@
 #include "feat.h"
 
 /*
- * The dccp_ctl_sk is the global socket data structure used for responding to
+ * The per-net dccp.v4_ctl_sk socket is used for responding to
  * the Out-of-the-blue (OOTB) packets. A control sock will be created
  * for this socket at the initialization time.
  */