ASoC: SOF: Intel: hda-stream: Do not dereference hstream until it is safe

Only access hext_stream->hstream after it has been checked for NULL pointer
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Link: https://lore.kernel.org/r/20230404092115.27949-2-peter.ujfalusi@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/intel/hda-stream.c

@@ -485,9 +485,8 @@ int hda_dsp_stream_hw_params(struct snd_sof_dev *sdev,
 {
 	const struct sof_intel_dsp_desc *chip = get_chip_info(sdev->pdata);
 	struct hdac_bus *bus = sof_to_bus(sdev);
-	struct hdac_stream *hstream = &hext_stream->hstream;
-	int sd_offset = SOF_STREAM_SD_OFFSET(hstream);
-	int ret;
+	struct hdac_stream *hstream;
+	int sd_offset, ret;
 	u32 dma_start = SOF_HDA_SD_CTL_DMA_START;
 	u32 mask;
 	u32 run;
@@ -502,6 +501,9 @@ int hda_dsp_stream_hw_params(struct snd_sof_dev *sdev,
 		return -ENODEV;
 	}
 
+	hstream = &hext_stream->hstream;
+	sd_offset = SOF_STREAM_SD_OFFSET(hstream);
+
 	/* decouple host and link DMA */
 	mask = 0x1 << hstream->index;
 	snd_sof_dsp_update_bits(sdev, HDA_DSP_PP_BAR, SOF_HDA_REG_PP_PPCTL,