audio: Fix the comment about threading of DriverInterface::init

'DriverInterface::init' is called on the same thread as other
interface methods (the worker thread), except
for 'setConnectedDevices'. Update the comment to reflect this,
and rearrange the methods order in the interface.

Bug: 283463913
Test: m
Change-Id: I8937506d20ff8233b4b934c421173ce2bec9d43e