tcp_memcontrol: fix reversed if condition

We should only dereference the pointer if it's valid, not the other way
round.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_memcontrol.c b/net/ipv4/tcp_memcontrol.c
index 171d7b6..7fed04f 100644
--- a/net/ipv4/tcp_memcontrol.c
+++ b/net/ipv4/tcp_memcontrol.c
@@ -44,7 +44,7 @@
 
 static void memcg_tcp_enter_memory_pressure(struct sock *sk)
 {
-	if (!sk->sk_cgrp->memory_pressure)
+	if (sk->sk_cgrp->memory_pressure)
 		*sk->sk_cgrp->memory_pressure = 1;
 }
 EXPORT_SYMBOL(memcg_tcp_enter_memory_pressure);