Update pcm doc strings
Update pcm doc strings

This is information I needed and is based on my understanding of information
from Takashi Iwai.

Signed-off-by: Takashi Iwai <4596b3305151c7ee743192a95d394341e3d3b644@suse.de>

takaswie/alsa-lib,zedongchen/alsa-lib,mengdonglin/alsa-lib,Distrotech/alsa-lib,takaswie/alsa-lib,zedongchen/alsa-lib,mengdonglin/alsa-lib,lgirdwood/alsa-lib,zedongchen/alsa-lib,mikelima/alsa-lib,zedongchen/alsa-lib,Distrotech/alsa-lib,mikelima/alsa-lib,takaswie/alsa-lib,alsa-project/alsa-lib,mikelima/alsa-lib,takaswie/alsa-lib,Distrotech/alsa-lib,tiwai/alsa-lib,mengdonglin/alsa-lib,tiwai/alsa-lib,takaswie/alsa-lib,mengdonglin/alsa-lib,zedongchen/alsa-lib,mikelima/alsa-lib,lgirdwood/alsa-lib,alsa-project/alsa-lib,alsa-project/alsa-lib,mikelima/alsa-lib,lgirdwood/alsa-lib,tiwai/alsa-lib,tiwai/alsa-lib,alsa-project/alsa-lib,lgirdwood/alsa-lib,Distrotech/alsa-lib,mengdonglin/alsa-lib,Distrotech/alsa-lib,lgirdwood/alsa-lib