ASoC: ti: Fix SDMA users not providing channel names

McBSP used to work correctly as long as compat DMA probing, removed by
commit 642aafea ("ASoC: ti: remove compat dma probing"), was
available.  New method of DMA probing apparently requires users to
provide channel names when registering with SDMA, while McBSP passes
NULLs.  Fix it.

The same probably applies to McASP (not tested), hence the patch fixes
both.

Fixes: 642aafea ("ASoC: ti: remove compat dma probing")
Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/ti/davinci-mcasp.c

@@ -2237,7 +2237,7 @@ static int davinci_mcasp_probe(struct platform_device *pdev)
 		ret = edma_pcm_platform_register(&pdev->dev);
 		break;
 	case PCM_SDMA:
-		ret = sdma_pcm_platform_register(&pdev->dev, NULL, NULL);
+		ret = sdma_pcm_platform_register(&pdev->dev, "tx", "rx");
 		break;
 	default:
 		dev_err(&pdev->dev, "No DMA controller found (%d)\n", ret);

sound/soc/ti/omap-mcbsp.c

@@ -1438,7 +1438,7 @@ static int asoc_mcbsp_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	return sdma_pcm_platform_register(&pdev->dev, NULL, NULL);
+	return sdma_pcm_platform_register(&pdev->dev, "tx", "rx");
 }
 
 static int asoc_mcbsp_remove(struct platform_device *pdev)