Bluetooth: Move mgmt related flags from hdev->flags to hdev->dev_flags

There's no point in exposing these to user-space (which is what happens
to everything in hdev->flags) so move them to dev_flags instead.

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