[ALSA] Removing obsolete AC97_SHARED_TYPES

This patch cleans last ac97 audio/modem codec interception in
initialization procedures (ac97_mixer_new()) and removes obsolete
SHARED_TYPE 'locking' which prevents from AMC codecs to function
correctly.

Signed-off-by: Sasha Khapyorsky <sashak@smlink.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>