V4L/DVB (7733): blackbird_find_mailbox negative return ignored in blackbird_initialize_codec()

dev->mailbox is unsigned. so a negative return goes unnoticed
Signed-off-by: Roel Kluin <12o3l@tiscali.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/cx88/cx88-blackbird.c

@@ -546,10 +546,12 @@ static int blackbird_initialize_codec(struct cx8802_dev *dev)
 		if (retval < 0)
 			return retval;
 
-		dev->mailbox = blackbird_find_mailbox(dev);
-		if (dev->mailbox < 0)
+		retval = blackbird_find_mailbox(dev);
+		if (retval < 0)
 			return -1;
 
+		dev->mailbox = retval;
+
 		retval = blackbird_api_cmd(dev, CX2341X_ENC_PING_FW, 0, 0); /* ping */
 		if (retval < 0) {
 			dprintk(0, "ERROR: Firmware ping failed!\n");