[TCP]: Use old definition of before

This reverts the new (unambiguous) definition of the TCP `before'
relation. As pointed out in an example by Herbert Xu, there is 
existing code which implicitly requires the old definition in order
to work correctly.
Signed-off-by: NGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -242,7 +242,7 @@ extern int tcp_memory_pressure;
 
 static inline int before(__u32 seq1, __u32 seq2)
 {
-        return (__s32)(seq2-seq1) > 0;
+        return (__s32)(seq1-seq2) < 0;
 }
 #define after(seq2, seq1) 	before(seq1, seq2)