ath6kl: check usb_register() return value

ath6kl_usb_init() does not check usb_register() return value.
As a result it may incorrectly report success of driver initialization.

Found by Linux Driver Verification project (linuxtesting.org).

kvalo: fix commit title and make cosmetic changes to the code to follow
more the style used in the driver
Signed-off-by: Marina Makienko <makienko@ispras.ru>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath6kl/usb.c

@@ -1196,7 +1196,14 @@ static struct usb_driver ath6kl_usb_driver = {
 
 static int ath6kl_usb_init(void)
 {
-	usb_register(&ath6kl_usb_driver);
+	int ret;
+
+	ret = usb_register(&ath6kl_usb_driver);
+	if (ret) {
+		ath6kl_err("usb registration failed: %d\n", ret);
+		return ret;
+	}
+
 	return 0;
 }