Bluetooth: Use defined link key size

Remove magic number with defined link key size.

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index 9fc7728..6c658fc 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -105,7 +105,7 @@
 	struct list_head list;
 	bdaddr_t bdaddr;
 	u8 type;
-	u8 val[16];
+	u8 val[HCI_LINK_KEY_SIZE];
 	u8 pin_len;
 };