RDS: cleanup: remove "== NULL"s and "!= NULL"s in ptr comparisons

Favor "if (foo)" style over "if (foo != NULL)".

Signed-off-by: Andy Grover <andy.grover@oracle.com>
diff --git a/net/rds/tcp_send.c b/net/rds/tcp_send.c
index a28b895..e5f6cce 100644
--- a/net/rds/tcp_send.c
+++ b/net/rds/tcp_send.c
@@ -226,7 +226,7 @@
 
 	read_lock(&sk->sk_callback_lock);
 	conn = sk->sk_user_data;
-	if (conn == NULL) {
+	if (!conn) {
 		write_space = sk->sk_write_space;
 		goto out;
 	}