Bluetooth: fix missing parameter for HCI_OP_DISCONNECT

The "dc" variable is initialized but not passed to hci_send_cmd().

Signed-off-by: Anderson Lizardo <anderson.lizardo@openbossa.org>
Signed-off-by: Bruna Moreira <bruna.moreira@openbossa.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>