ASoC: SOF: topology: remove unnecessary memory alloc for sdev->private

ASoC: SOF: topology: remove unnecessary memory alloc for sdev->private

Looks like it was left over from the previous implementation of
DMIC PDM token parsing. It is not used anymore.

Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200824200912.46852-4-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>