ASoC: ti: davinci-mcasp: Fix fall-through warning for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a warning
by explicitly adding a fallthrough; statement.

Link: https://github.com/KSPP/linux/issues/115
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Acked-by: Peter Ujfalusi <peter.ujflausi@gmail.com>
Link: https://lore.kernel.org/r/20210604072714.GA244640@embeddedor
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/ti/davinci-mcasp.c

@@ -2317,6 +2317,7 @@ static int davinci_mcasp_probe(struct platform_device *pdev)
 		break;
 	default:
 		dev_err(&pdev->dev, "No DMA controller found (%d)\n", ret);
+		fallthrough;
 	case -EPROBE_DEFER:
 		goto err;
 	}