greybus: audio: codec driver cleanup

audio codec driver is now moved to bundle driver approach.
This resolved many race conditions related to audio mgmt &
data connection init/exit sequence.
Thus, a lot of helper functions can now be safely removed.

Signed-off-by: Vaibhav Agarwal <vaibhav.agarwal@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>