Revert "ALSA: pcm: Use SG-buffer only when direct DMA is available"

This reverts commit 3ad796cb ("ALSA: pcm: Use SG-buffer only when
direct DMA is available") also the modification commit 467fd0e8
("ALSA: pcm: Fix build error on m68k and others").

Poking the DMA internal helper is a layer violation, so we should
avoid that.  Meanwhile the actual bug has been addressed by the
Kconfig fix in commit dbed452a ("dma-pool: decouple DMA_REMAP from
DMA_COHERENT_POOL"), so we can live without this hack.

Link: https://lore.kernel.org/r/20200717064130.22957-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/pcm_memory.c

@@ -11,7 +11,6 @@
 #include <linux/moduleparam.h>
 #include <linux/vmalloc.h>
 #include <linux/export.h>
-#include <linux/dma-mapping.h>
 #include <sound/core.h>
 #include <sound/pcm.h>
 #include <sound/info.h>
@@ -41,19 +40,6 @@ static int do_alloc_pages(struct snd_card *card, int type, struct device *dev,
 	    card->total_pcm_alloc_bytes + size > max_alloc_per_card)
 		return -ENOMEM;
 
-
-#ifdef CONFIG_SND_DMA_SGBUF
-	if ((type == SNDRV_DMA_TYPE_DEV_SG || type == SNDRV_DMA_TYPE_DEV_UC_SG) &&
-	    !dma_is_direct(get_dma_ops(dev))) {
-		/* mutate to continuous page allocation */
-		dev_dbg(dev, "Use continuous page allocator\n");
-		if (type == SNDRV_DMA_TYPE_DEV_SG)
-			type = SNDRV_DMA_TYPE_DEV;
-		else
-			type = SNDRV_DMA_TYPE_DEV_UC;
-	}
-#endif /* CONFIG_SND_DMA_SGBUF */
-
 	err = snd_dma_alloc_pages(type, dev, size, dmab);
 	if (!err) {
 		mutex_lock(&card->memory_mutex);