HDMI eld infromation via debugfs/procefs support

[kv2019i]

The legacy/AZX driver exposes wealth of debug information related to HDMI audio via /proc/asound/eld* entries.

This is widely adopted as a standard part of debugging HDMI audio issues. E.g. bugs like
https://bugs.freedesktop.org/show_bug.cgi?id=110932

SOF does not currently implement this interface, which will create problems with users moving from legacy driver to SOF.

FYI list: @wenqingfu @libinyang @xiulipan

[kv2019i]

This is implemented in usptream and sof-dev via use of common HDMI driver. Closing.