Bluetooth: Rework le_scan_restart for hci_sync

le_scan_restart delayed work queue was running as a deprecated
hci_request instead of on the newer thread-safe hci_sync mechanism.

Signed-off-by: Brian Gix <brian.gix@intel.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>