Bluetooth: Use whitelist for scan policy when suspending

Even with one advertisement monitor in place, the scan policy should use
the whitelist while the system is going to suspend to prevent waking by
random advertisement.

The following test was performed.
- With a paired device, register one advertisement monitor, suspend
the system and verify that the host was not awaken by random
advertisements.

Signed-off-by: Miao-chen Chou <mcchou@chromium.org>
Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>