ASoC: SOF: Intel: hda-dai: Drop misleading comment regarding dma_data

The comment in hda_link_dma_hw_params() is no longer valid as the dma_data
is set to NULL at system suspend as well.

Instead of rewording the comment to state the obvious: try to take the
hext_stream from the dma_data and if it is not set then assign a new one
and store it as dma_data.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20220712131620.13365-2-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>