ASoC: Intel: remove misleading DMA error messages on Baytrail platforms

During probe, the Baytrail audio driver reports errors such as:

[44.172040] baytrail-pcm-audio baytrail-pcm-audio: error: invalid DMA engine 0
[44.172137] baytrail-pcm-audio baytrail-pcm-audio: sst_dma_new failed

Those error messages are misleading, there is no error since the DMA
is explicitly not configured for Baytrail.
Add a test to remove DMA error checks when DMA is not configured
and return silently.

Acked-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/sst-acpi.c

@@ -142,6 +142,7 @@ static int sst_acpi_probe(struct platform_device *pdev)
 	sst_acpi->desc = desc;
 	sst_acpi->mach = mach;
 
+	sst_pdata->resindex_dma_base = desc->resindex_dma_base;
 	if (desc->resindex_dma_base >= 0) {
 		sst_pdata->dma_engine = desc->dma_engine;
 		sst_pdata->dma_base = desc->resindex_dma_base;

sound/soc/intel/sst-dsp.h

@@ -206,6 +206,7 @@ struct sst_pdata {
 	const struct firmware *fw;
 
 	/* DMA */
+	int resindex_dma_base; /* other fields invalid if equals to -1 */
 	u32 dma_base;
 	u32 dma_size;
 	int dma_engine;

sound/soc/intel/sst-firmware.c

@@ -271,6 +271,10 @@ int sst_dma_new(struct sst_dsp *sst)
 	const char *dma_dev_name;
 	int ret = 0;
 
+	if (sst->pdata->resindex_dma_base == -1)
+		/* DMA is not used, return and squelsh error messages */
+		return 0;
+
 	/* configure the correct platform data for whatever DMA engine
 	* is attached to the ADSP IP. */
 	switch (sst->pdata->dma_engine) {