greybus: audio: Enable audio path based on control switch state only

As per current implementation, audio data is played from each individual
SPK module connected to endo frame. This is not a valid requirement in
case of capture/headset path. So, provide a mechanism to enable
individual module path based on it's control switch state.

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