ALSA: Fix SG-buffer DMA with non-coherent architectures

Using SG-buffers with dma_alloc_coherent() is often very inefficient
on non-coherent architectures because a tracking record could be
allocated in addition for each dma_alloc_coherent() call.
Instead, simply disable SG-buffers but just allocate normal continuous
buffers on non-supported (currently all but x86) architectures.

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

sound/core/Makefile

@@ -13,7 +13,7 @@ snd-pcm-objs := pcm.o pcm_native.o pcm_lib.o pcm_timer.o pcm_misc.o \
 		pcm_memory.o
 
 snd-page-alloc-y := memalloc.o
-snd-page-alloc-$(CONFIG_HAS_DMA) += sgbuf.o
+snd-page-alloc-$(CONFIG_SND_DMA_SGBUF) += sgbuf.o
 
 snd-rawmidi-objs  := rawmidi.o
 snd-timer-objs    := timer.o