wil6210: fix a warning message condition

"iter" is -1 at the end of the loop and not zero.  It means we don't
print a warning message.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/wil6210/main.c

@@ -987,7 +987,7 @@ int __wil_down(struct wil6210_priv *wil)
 	}
 	mutex_lock(&wil->mutex);
 
-	if (!iter)
+	if (iter < 0)
 		wil_err(wil, "timeout waiting for idle FW/HW\n");
 
 	wil_reset(wil, false);