[Bluetooth] Add support for handling simple eSCO links

With the Bluetooth 1.2 specification the Extended SCO feature for
better audio connections was introduced. So far the Bluetooth core
wasn't able to handle any eSCO connections correctly. This patch
adds simple eSCO support while keeping backward compatibility with
older devices.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>