Bluetooth: Fix storing negative values as unsigned char

This is mostly cleanup. There is only one caller and it just checks for
non-zero return values. Still "ret" should be int because we want to return
-EINVAL on errors.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/drivers/bluetooth/btmrvl_main.c b/drivers/bluetooth/btmrvl_main.c
index 53a43ad..49ec89c 100644
--- a/drivers/bluetooth/btmrvl_main.c
+++ b/drivers/bluetooth/btmrvl_main.c
@@ -66,7 +66,7 @@
 {
 	struct btmrvl_adapter *adapter = priv->adapter;
 	struct btmrvl_event *event;
-	u8 ret = 0;
+	int ret = 0;
 
 	event = (struct btmrvl_event *) skb->data;
 	if (event->ec != 0xff) {