net: tcp2: Fixed IS_ENABLED check for NET_TCP_MAX_SEND_WINDOW_SIZE

The #if statement used IS_ENABLED to check if it was defined.
IS_ENABLED will only return true if the value is 1, and false otherwise.
If the NET_TCP_MAX_SEND_WINDOW_SIZE value would be e.g. 8, then the
check would fail.

Signed-off-by: Emil Gydesen <[email protected]>

Author: Thalley

subsys/net/ip/tcp2.c

@@ -1503,7 +1503,7 @@ static void tcp_in(struct tcp *conn, struct net_pkt *pkt)
 
 		conn->send_win = ntohs(th_win(th));
 
-#if IS_ENABLED(CONFIG_NET_TCP_MAX_SEND_WINDOW_SIZE)
+#if defined(CONFIG_NET_TCP_MAX_SEND_WINDOW_SIZE)
 		if (CONFIG_NET_TCP_MAX_SEND_WINDOW_SIZE) {
 			max_win = CONFIG_NET_TCP_MAX_SEND_WINDOW_SIZE;
 		} else