Bluetooth: Fix issue with switching BR/EDR back on when disabled

For dual-mode controllers it is possible to disable BR/EDR and operate
as LE single mode controllers with a static random address. If that is
the case, then refuse switching BR/EDR back on after the controller has
been powered.

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