ASoC: sprd: use asoc_substream_to_rtd()

Now we can use asoc_substream_to_rtd() macro,
let's use it.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87y2nfyoes.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sprd/sprd-pcm-dma.c

@@ -190,7 +190,7 @@ static int sprd_pcm_hw_params(struct snd_soc_component *component,
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct sprd_pcm_dma_private *dma_private = runtime->private_data;
-	struct snd_soc_pcm_runtime *rtd = substream->private_data;
+	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
 	struct sprd_pcm_dma_params *dma_params;
 	size_t totsize = params_buffer_bytes(params);
 	size_t period = params_period_bytes(params);