Bluetooth: Allow changing device class when BR/EDR is disabled

Changing the device class when BR/EDR is disabled has no visible
effect for remote devices. However to simplify the logic allow it
as long as the controller supports BR/EDR operations.

If it is not allowed, then the overall logic becomes rather
complicated since the class of device values would need clearing
or restoring when BR/EDR setting changes.

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