commit 413cbf46 upstream.

AMD/ATI HDMI controller chip models, we already have a filter to lower
to 32bit DMA, but the rest are supposed to be working with 64bit
although the hardware doesn't really work with 63bit but only with 40
or 48bit DMA.  In this patch, we take 40bit DMA for safety for the
AMD/ATI controllers as the graphics drivers does.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[ luis: backported to 3.16:
  - replaced AZX_GCAP_64OK by ICH6_GCAP_64OK ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>