Bluetooth: Update advertising data based on management commands

Magically updating the advertising data when some random command enables
advertising in the controller is not really a good idea. It also caused
a bit of complicated code with the exported hci_udpate_ad function that
is shared from many places.

This patch consolidates the advertising data update into the management
core. It also makes sure that when powering on with LE enabled or later
on enabling LE the controller has a good default for advertising data.

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