Bluetooth: Add missing check for BREDR_ENABLED flag in update_class()

We shouldn't be sending the HCI_Write_Class_Of_Device command when
BR/EDR is disabled since this is a BR/EDR-only command.

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