ALSA: kernel docs: fix sound/core/ kernel-doc

Add kernel-doc function short descriptions to sound/core functions that
are missing this short description.  Mostly this involves moving some of
the function description onto the @funcname line.

Also correct a few variable names and fix other kernel-doc notation.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>