net/tipc/subscr.c: don't use ___constant_swab32

It's an internal implementation detail which we _should_ be free to change. 
So we did, and it promptly broke.

The compiler shold be able to work out when to use the __constant version
anyway.
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/subscr.c

@@ -85,7 +85,7 @@ static struct top_srv topsrv = { 0 };
 
 static u32 htohl(u32 in, int swap)
 {
-	return swap ? (u32)___constant_swab32(in) : in;
+	return swap ? swab32(in) : in;
 }
 
 /**