ASoC: atmel: mchp-pdmc: Skip ALSA restoration if substream runtime is uninitialized

Update the driver to prevent alsa-restore.service from failing when
reading data from /var/lib/alsa/asound.state at boot. Ensure that the
restoration of ALSA mixer configurations is skipped if substream->runtime
is NULL.

Fixes: 50291652 ("ASoC: atmel: mchp-pdmc: add PDMC driver")
Signed-off-by: Andrei Simion <andrei.simion@microchip.com>
Link: https://patch.msgid.link/20240924081237.50046-1-andrei.simion@microchip.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/atmel/mchp-pdmc.c

@@ -302,6 +302,9 @@ static int mchp_pdmc_chmap_ctl_put(struct snd_kcontrol *kcontrol,
 	if (!substream)
 		return -ENODEV;
 
+	if (!substream->runtime)
+		return 0; /* just for avoiding error from alsactl restore */
+
 	map = mchp_pdmc_chmap_get(substream, info);
 	if (!map)
 		return -EINVAL;