[PATCH] ALSA: hda/hdmi: Add Intel silent stream support

[Pierre-Louis Bossart]

>>> The silent stream is enabled with a Kconfig option, as well as a kernel
>>> parameter should there be a need to override the build time default.
>>
>> I'm not sure whether the module option is the best interface.
>> An alternative is a mixer element that controls dynamically.  Then
>> it'll be per card unlike the module option.
> 
> +1, kcontrol seems the appropriate way to control this.

It was my suggestion to use Kconfig+kernel parameter for 
simplicity/overrides.

The kcontrol is a nice idea, but in practice we typically only have one 
card dealing with HDMI. It also doesn't have a UCM representation so 
would force the use of amixer and manual configs, or the UCM file would 
always set the mode.