ASoC: stm32: sai: fix exposed capabilities in spdif mode

Change capabilities exposed in SAI S/PDIF mode, to match
actually supported formats.
In S/PDIF mode only 32 bits stereo is supported.
Signed-off-by: Olivier Moysan <olivier.moysan@st.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/stm/stm32_sai_sub.c

@@ -682,6 +682,14 @@ static int stm32_sai_startup(struct snd_pcm_substream *substream,
 
 	sai->substream = substream;
 
+	if (STM_SAI_PROTOCOL_IS_SPDIF(sai)) {
+		snd_pcm_hw_constraint_mask64(substream->runtime,
+					     SNDRV_PCM_HW_PARAM_FORMAT,
+					     SNDRV_PCM_FMTBIT_S32_LE);
+		snd_pcm_hw_constraint_single(substream->runtime,
+					     SNDRV_PCM_HW_PARAM_CHANNELS, 2);
+	}
+
 	ret = clk_prepare_enable(sai->sai_ck);
 	if (ret < 0) {
 		dev_err(cpu_dai->dev, "Failed to enable clock: %d\n", ret);