ath10k: Change the warning message string

The "WARNING" string confuses syzbot, which thinks it found
a crash [1].

Change the string to avoid such problem.

[1] https://lkml.org/lkml/2019/5/9/243

Reported-by: syzbot+c1b25598aa60dcd47e78@syzkaller.appspotmail.com
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ath/ath10k/usb.c

@@ -1016,7 +1016,7 @@ static int ath10k_usb_probe(struct usb_interface *interface,
 	}
 
 	/* TODO: remove this once USB support is fully implemented */
-	ath10k_warn(ar, "WARNING: ath10k USB support is incomplete, don't expect anything to work!\n");
+	ath10k_warn(ar, "Warning: ath10k USB support is incomplete, don't expect anything to work!\n");
 
 	return 0;