Bluetooth: Rename hci_acl_disconn

As hci_acl_disconn function basically sends the HCI Disconnect Command
and it is used to disconnect ACL, SCO and LE links, renaming it to
hci_disconnect is more suitable.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>