UCM fixes and extensions, 2nd round
This patch set fixes:
- the device values are obtained via the UCM mechanism (with the defined fallbacks inside UCM API)
- handle the mixer / jack device names (we may use multi-card UCMs in future)
- remove some (wrong) assumptions
- cache mixer access
- add support for HDMI ELD like for the "legacy" alsa probe
- do not create mixers for sink/sound when there are no UCM volume paths (do the check more early)