ALSA: hda - Add support of auto-parser to cxt5047 / CX20551 Waikiki

Similarly like other Conexant codecs, now model=auto is supported for
cxt5047.

But the auto-parser mode isn't activated as default yet, since BIOS
pin-configs seem often broken on machines with this codec.  User need
to pass model=auto explicitly.

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