ASoC: apple: mca: Improve handling of unavailable DMA channels

When we fail to obtain a DMA channel, don't return a blanket -EINVAL,
instead return the original error code if there's one. This makes
deferring work as it should. Also don't print an error message for
-EPROBE_DEFER.

Fixes: 4ec8179 ("ASoC: apple: mca: Postpone requesting of DMA channels")
Signed-off-by: Martin Povišer <povik+lin@cutebit.org>
Link: https://lore.kernel.org/r/20230224153302.45365-3-povik+lin@cutebit.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: povik

sound/soc/apple/mca.c

@@ -950,10 +950,17 @@ static int mca_pcm_new(struct snd_soc_component *component,
 		chan = mca_request_dma_channel(cl, i);
 
 		if (IS_ERR_OR_NULL(chan)) {
+			mca_pcm_free(component, rtd->pcm);
+
+			if (chan && PTR_ERR(chan) == -EPROBE_DEFER)
+				return PTR_ERR(chan);
+
 			dev_err(component->dev, "unable to obtain DMA channel (stream %d cluster %d): %pe\n",
 				i, cl->no, chan);
-			mca_pcm_free(component, rtd->pcm);
-			return -EINVAL;
+
+			if (!chan)
+				return -EINVAL;
+			return PTR_ERR(chan);
 		}
 
 		cl->dma_chans[i] = chan;