ALSA: hda - Re-define snd_hda_parse_nid_path()

This commit modifies the definition of snd_hda_parse_nid_path()
slightly, now with_aa_mix argument is changed to anchor_nid, so that
it can handle any NID generically as an anchor point to include or
exclude.

The with_aa_mix field in struct nid_path is removed again by this
change.

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