ALSA: pcm: Fix build error on m68k and others

The commit 3ad796cb ("ALSA: pcm: Use SG-buffer only when direct
DMA is available") introduced a check of the DMA type and this caused
a build error on m68k (and possibly some others) due to the lack of
dma_is_direct() definition.  Since the check is needed only for
CONFIG_SND_DMA_SGBUF enablement (i.e. solely x86), use #ifdef instead
of IS_ENABLED() for avoiding such a build error.

Fixes: 3ad796cb ("ALSA: pcm: Use SG-buffer only when direct DMA is available")
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/r/20200707111225.26826-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/pcm_memory.c

@@ -41,8 +41,9 @@ 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;
 
-	if (IS_ENABLED(CONFIG_SND_DMA_SGBUF) &&
-	    (type == SNDRV_DMA_TYPE_DEV_SG || type == SNDRV_DMA_TYPE_DEV_UC_SG) &&
+
+#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");
@@ -51,6 +52,7 @@ static int do_alloc_pages(struct snd_card *card, int type, struct device *dev,
 		else
 			type = SNDRV_DMA_TYPE_DEV_UC;
 	}
+#endif /* CONFIG_SND_DMA_SGBUF */
 
 	err = snd_dma_alloc_pages(type, dev, size, dmab);
 	if (!err) {