Second argument of these functions has three different names in
documentation/header/code (obj/control/value). This easily causes users'
confusion.
This commit applies consistent names for the arguments.
Fixes: 90020c05f8 ('ctl: improve comments for handling element data')
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>