CHROMIUM: ASoC: Byt-max98090: Add byt_max98090_stop method

Put the codec into shutdown when all streams have been stopped.

[Jarkko: Forward ported on top of updated sst-baytrail-ipc.c]

Signed-off-by: Kevin Strasser <kevin.strasser@intel.com>
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Revert "CHROMIUM: ASoC: Byt-max98090: Add byt_max98090_stop method"

This reverts commit 54d7a366e2be510341bc93453dc138f1333c4c45.

I don't think we need above patch. I guess same effect can be achieved by
setting codec pmdown_time to zero:

echo 0 >/sys/devices/platform/80860F28\:00/byt-max98090/Baytrail\Audio/pmdown_time

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>