Bluetooth: Update start_discovery to use HCI request

This patch modifies the start_discovery function so it uses the new
HCI request framework.

We build the HCI request according to the discovery type (add inquiry
and LE scan HCI commands) and run the HCI request. We also register
the start_discovery_complete request callback which handles all mgmt
command status and command complete events for this command.

This way, we move all start_discovery mgmt handling code spread in
hci_event.c to a single place in mgmt.c.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Bluetooth: Remove start discovery handling from hci_event.c

Since all mgmt start discovery command status and command complete
events are now handled in start_discovery_complete callback in mgmt.c,
we can remove this handling from hci_event.c.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Bluetooth: Update stop_discovery to use HCI request

This patch modifies the stop_discovery function so it uses the new
HCI request framework.

We build the HCI request according to the current discovery state
and run the HCI request. We also register the stop_discovery_complete
request callback which handles all mgmt command status and command
complete events for mgmt stop discovery command.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Bluetooth: Remove stop discovery handling from hci_event.c

Since all mgmt stop discovery command status and command complete
events are now handled in stop_discovery_complete callback in mgmt.c,
we can remove this handling from hci_event.c.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>