Bluetooth: Fix handling of experimental feature for codec offload

The existence of the experimental feature identifiy is the indication
that it is supported or not. No extra flag needed and the initial flag
should define if a feature is enabled or not. This is actually defined
in the management API definition.

Fixes: ad933151 ("Bluetooth: Add offload feature under experimental flag")
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>