Bluetooth: hci_sync: Rework background scan

This replaces the use of hci_update_background_scan with
hci_update_passive_scan which runs from cmd_work_sync and deal properly
with resolving list when LL privacy is enabled.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>