ASoC: Intel: catpt: use asoc_substream_to_rtd()

Now we can use asoc_substream_to_rtd() macro,
let's use it.

Signed-off-by: Lianjie Zhang <zhanglianjie@uniontech.com>
Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Link: https://lore.kernel.org/r/20220307151939.32870-1-zhanglianjie@uniontech.com


Signed-off-by: Mark Brown <broonie@kernel.org>