Bluetooth: Fix updating advertising state flags and data

This patch adds a callback for the HCI_LE_Set_Advertise_Enable command.
The callback is responsible for updating the HCI_LE_PERIPHERAL flag
updating as well as updating the advertising data flags field to
indicate undirected connectable advertising.

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>