Bluetooth: Remove unnecessary stop_scan_complete function

The stop_scan_complete function was used as an intermediate step before
doing the actual connection creation. Since we're using hci_request
there's no reason to have this extra function around, i.e. we can simply
put both HCI commands into the same request.

The single task that the intermediate function had, i.e. indicating
discovery as stopped is now taken care of by a new
HCI_LE_SCAN_INTERRUPTED flag which allows us to do the discovery state
update when the stop scan command completes.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>