NFC: delete null dereference

The exit label performs device_unlock(&dev->dev);, which will fail when dev
is NULL, and nfc_put_device(dev);, which is not useful when dev is NULL, so
just exit the function immediately.

Problem found using scripts/coccinelle/null/deref_null.cocci
Signed-off-by: NJulia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>

net/nfc/netlink.c

@@ -1109,10 +1109,8 @@ static int nfc_genl_llc_sdreq(struct sk_buff *skb, struct genl_info *info)
 	idx = nla_get_u32(info->attrs[NFC_ATTR_DEVICE_INDEX]);
 
 	dev = nfc_get_device(idx);
-	if (!dev) {
-		rc = -ENODEV;
-		goto exit;
-	}
+	if (!dev)
+		return -ENODEV;
 
 	device_lock(&dev->dev);