Bluetooth: Fix accepting set_dev_class for non-BR/EDR controllers

The concept of Class of Device only exists for BR/EDR controllers. The
mgmt_set_dev_class command should therefore return a proper "not
supported" error if it is attempted for a controller that doesn't
support BR/EDR (e.g. a single mode LE-only one).

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>