[NET]: Name magic constants in sock_wake_async()

The sock_wake_async() performs a bit different actions
depending on "how" argument. Unfortunately this argument
ony has numerical magic values.

I propose to give names to their constants to help people
reading this function callers understand what's going on
without looking into this function all the time.

I suppose this is 2.6.25 material, but if it's not (or the
naming seems poor/bad/awful), I can rework it against the
current net-2.6 tree.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/output.c b/net/dccp/output.c
index f495446..33ce737 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -170,7 +170,7 @@
 		wake_up_interruptible(sk->sk_sleep);
 	/* Should agree with poll, otherwise some programs break */
 	if (sock_writeable(sk))
-		sk_wake_async(sk, 2, POLL_OUT);
+		sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
 
 	read_unlock(&sk->sk_callback_lock);
 }