ASoC: SOF: ipc4-pcm: fix possible null pointer deference

The call to snd_sof_find_spcm_dai() could return NULL,
add nullable check for the return value to avoid null
pointer defenrece.

Fixes: 7cb1900 ("ASoC: SOF: ipc4-pcm: add hw_params")
Signed-off-by: Chao Song <chao.song@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://lore.kernel.org/r/20230816133311.7523-1-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Chao Song

sound/soc/sof/ipc4-pcm.c

@@ -708,6 +708,9 @@ static int sof_ipc4_pcm_hw_params(struct snd_soc_component *component,
 	struct snd_sof_pcm *spcm;
 
 	spcm = snd_sof_find_spcm_dai(component, rtd);
+	if (!spcm)
+		return -EINVAL;
+
 	time_info = spcm->stream[substream->stream].private;
 	/* delay calculation is not supported by current fw_reg ABI */
 	if (!time_info)