ctl: improve API documentation for TLV operation
ctl: improve API documentation for TLV operation

A commit fe1b08803db6 ("ctl: improve API documentation for threshold level
operations") changes documentations for some TLV-related APIs with wrong
explanations.

This commit fix it with better explanations.

Fixes: fe1b08803db6 ("ctl: improve API documentation for threshold level operations")
Signed-off-by: Takashi Sakamoto <d5ec7d0cd8074757a1f5eb708bc105c3065a65ea@sakamocchi.jp>
Signed-off-by: Takashi Iwai <4596b3305151c7ee743192a95d394341e3d3b644@suse.de>

tiwai/alsa-lib,tiwai/alsa-lib,alsa-project/alsa-lib,alsa-project/alsa-lib,alsa-project/alsa-lib,takaswie/alsa-lib,tiwai/alsa-lib,tiwai/alsa-lib,alsa-project/alsa-lib,takaswie/alsa-lib,takaswie/alsa-lib,takaswie/alsa-lib,takaswie/alsa-lib