Bluetooth: Fix encryption key size handling for LTKs

The encryption key size for LTKs is supposed to be applied only at the
moment of encryption. When generating a Link Key (using LE SC) from
the LTK the full non-shortened value should be used. This patch
modifies the code to always keep the full value around and only apply
the key size when passing the value to HCI.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index ee5e598..2c48bf0 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -276,7 +276,7 @@
 }
 
 void hci_le_start_enc(struct hci_conn *conn, __le16 ediv, __le64 rand,
-		      __u8 ltk[16])
+		      __u8 ltk[16], __u8 key_size)
 {
 	struct hci_dev *hdev = conn->hdev;
 	struct hci_cp_le_start_enc cp;
@@ -288,7 +288,7 @@
 	cp.handle = cpu_to_le16(conn->handle);
 	cp.rand = rand;
 	cp.ediv = ediv;
-	memcpy(cp.ltk, ltk, sizeof(cp.ltk));
+	memcpy(cp.ltk, ltk, key_size);
 
 	hci_send_cmd(hdev, HCI_OP_LE_START_ENC, sizeof(cp), &cp);
 }