ALSA: atiixp: fix fall-through annotations

Replace "fallthru" with a proper "fall through" annotation.

This fix is part of the ongoing efforts to enabling
-Wimplicit-fallthrough
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/atiixp.c

@@ -903,15 +903,15 @@ static int snd_atiixp_playback_prepare(struct snd_pcm_substream *substream)
 	case 8:
 		data |= ATI_REG_OUT_DMA_SLOT_BIT(10) |
 			ATI_REG_OUT_DMA_SLOT_BIT(11);
-		/* fallthru */
+		/* fall through */
 	case 6:
 		data |= ATI_REG_OUT_DMA_SLOT_BIT(7) |
 			ATI_REG_OUT_DMA_SLOT_BIT(8);
-		/* fallthru */
+		/* fall through */
 	case 4:
 		data |= ATI_REG_OUT_DMA_SLOT_BIT(6) |
 			ATI_REG_OUT_DMA_SLOT_BIT(9);
-		/* fallthru */
+		/* fall through */
 	default:
 		data |= ATI_REG_OUT_DMA_SLOT_BIT(3) |
 			ATI_REG_OUT_DMA_SLOT_BIT(4);