Recent AMD HDMI codecs (revision ID 3 and later, 0x100300 as reported by
procfs codec#0) have a configurable ramp-up/down functionality.

The documentation ( http://www.x.org/docs/AMD/AMD_HDA_verbs_v2.pdf )
specifies that 180 ("180/256 =~ 0.7") is recommended for PCM and 0 for
non-PCM.

Apply the recommended values according to provided S/PDIF AES0 settings
since ramp-up/down does not make sense for non-PCM.

v2: adapted to hdmi_ops infrastructure

* More note from Anssi:
actually, re-reading mails reveals that Olivier didn't find the
expected difference with this setting, except for "maybe slightly
slower startup with AES0=6" (i.e. value 0, which is unexpected).

So maybe
a) it makes too unnoticiable a difference, or
b) only affects certain hardware (card and/or sink), or
c) ramp-up/down is only triggered with the MUTE bit of
   ATI_VERB_SET_MULTICHANNEL_xx which is also rev3+ specific,
   but is not presently used by the driver,
or something else.

So there's a significant chance setting ramp rate is useless for us ATM,
but probably does not do actual harm either.
Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
Tested-by: Olivier Langlois <olivier@trillion01.com> # v1
Signed-off-by: Takashi Iwai <tiwai@suse.de>