ALSA: docs: Drop snd_print*() stuff

The legacy snd_print*() helpers will be dropped now.  Clean up the
corresponding documentation, too.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20240807133452.9424-54-tiwai@suse.de