esp4: remove assignment in if condition

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 360b565..d2bf02e 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -392,8 +392,10 @@
 	if (elen <= 0)
 		goto out;
 
-	if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
+	err = skb_cow_data(skb, 0, &trailer);
+	if (err < 0)
 		goto out;
+
 	nfrags = err;
 
 	assoclen = sizeof(*esph);