For proper control of the AD update and the related HCI commands it's
best to run the AD update through an async request instead of a
standalone HCI command. This patch changes the hci_update_ad() function
to take a request pointer and updates its users appropriately. E.g. the
function is no longer called after the init sequence but during stage 3
of the init sequence.

The TX power is read during the init sequence, so we don't need an
explicit update whenever it is read and the AD update based on the local
name should be done through the local name mgmt handler. The only other
user is the update based on enabling advertising. This part is still
kept as there is no mgmt API to enable it.
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>