ALSA: hda - Enable snoop bit for AMD controllers

AMD Hudson controllers give noisy outputs when the buffer data is
rewritten on the fly as PulseAudio does.  This seems fixed by the
snoop bit enabled just like ATI chipset.

Also, disable 64bit DMA as now, to be sure.
We can revisit this later.

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