ALSA: hda - hdmi: Add ELD emulation for ATI/AMD codecs

ALSA: hda - hdmi: Add ELD emulation for ATI/AMD codecs

ATI/AMD HDMI/DP codecs do not include standard HDA ELD (EDID-like data)
support.

In place of providing access to an ELD buffer, various vendor-specific
verbs are provided to provide the relevant information. Revision ID 3
and later (0x100300 as reported by procfs codec#X) have support for
providing more information than the previous revisions (but only if
supported by the display driver).

Generate ELD from the information provided by the vendor-specific verbs
on ATI/AMD codecs.

The specification is available at:
http://www.x.org/docs/AMD/AMD_HDA_verbs_v2.pdf

v2: moved code to hda_eld.c and cleaned it up
v3: adapted to hdmi_ops infrastructure

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
Tested-by: Peter Frühberger <fritsch@xbmc.org> # v2
Tested-by: Olivier Langlois <olivier@trillion01.com> # v2
Signed-off-by: Takashi Iwai <tiwai@suse.de>