Bluetooth: Remove unused function

Remove the function hci_conn_change_link_key() that is not used anywhere.

This was partially found by using a static code analysis program called
cppcheck.
Signed-off-by: NRickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: NJohan Hedberg <johan.hedberg@intel.com>

include/net/bluetooth/hci_core.h

@@ -781,7 +781,6 @@ int hci_conn_check_link_mode(struct hci_conn *conn);
 int hci_conn_check_secure(struct hci_conn *conn, __u8 sec_level);
 int hci_conn_security(struct hci_conn *conn, __u8 sec_level, __u8 auth_type,
 		      bool initiator);
-int hci_conn_change_link_key(struct hci_conn *conn);
 int hci_conn_switch_role(struct hci_conn *conn, __u8 role);
 
 void hci_conn_enter_active_mode(struct hci_conn *conn, __u8 force_active);

net/bluetooth/hci_conn.c

@@ -1084,21 +1084,6 @@ int hci_conn_check_secure(struct hci_conn *conn, __u8 sec_level)
 }
 EXPORT_SYMBOL(hci_conn_check_secure);
 
-/* Change link key */
-int hci_conn_change_link_key(struct hci_conn *conn)
-{
-	BT_DBG("hcon %p", conn);
-
-	if (!test_and_set_bit(HCI_CONN_AUTH_PEND, &conn->flags)) {
-		struct hci_cp_change_conn_link_key cp;
-		cp.handle = cpu_to_le16(conn->handle);
-		hci_send_cmd(conn->hdev, HCI_OP_CHANGE_CONN_LINK_KEY,
-			     sizeof(cp), &cp);
-	}
-
-	return 0;
-}
-
 /* Switch role */
 int hci_conn_switch_role(struct hci_conn *conn, __u8 role)
 {