Bluetooth: Make connect / disconnect cfm functions return void

Return values are never used because callers hci_proto_connect_cfm
and hci_proto_disconn_cfm return void.

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>