ALSA: memalloc: Add fall-through annotation

As a preparatory patch for the upcoming -Wimplicit-fallthrough
compiler checks, add the "fall through" annotation in
snd_dma_alloc_pages().  Note that this seems necessary to be put
exactly before the next label, so it's outside the ifdef block.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/memalloc.c

@@ -203,6 +203,7 @@ int snd_dma_alloc_pages(int type, struct device *device, size_t size,
 		 */
 		dmab->dev.type = SNDRV_DMA_TYPE_DEV;
 #endif /* CONFIG_GENERIC_ALLOCATOR */
+		/* fall through */
 	case SNDRV_DMA_TYPE_DEV:
 	case SNDRV_DMA_TYPE_DEV_UC:
 		snd_malloc_dev_pages(dmab, size);