[ALSA] Use dma_alloc_coherent() hack on i386 only

Modules: Memalloc module

Use dma_alloc_coherent() hack on i386 only (as a valid arch).
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/memalloc.c

@@ -83,7 +83,7 @@ struct snd_mem_list {
  *  Hacks
  */
 
-#if defined(__i386__) || defined(__ppc__) || defined(__x86_64__)
+#if defined(__i386__)
 /*
  * A hack to allocate large buffers via dma_alloc_coherent()
  *