Bluetooth: Remove inquiry helpers

This patch removes hci_do_inquiry and hci_cancel_inquiry helpers. We
now use the HCI request framework in device discovery functionality
and these helpers are no longer needed.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Acked-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>