ALSA: hda - Use standard fixup table for STAC927x

This conversion is a bit tricky.  Since STAC927x may take two
different volume-knob initialization values depending on the model, a
new flag, spec->volknob_init, is introduced to indicate whether it's
the standard volume-knob initialization or not.

Also, Dell BIOS model is now directly mapped onto the fixup table
instead of parsing in the function.  This resulted in a new model ref,
STAC_927X_DELL_BIOS_SPDIF, which is a chained entry.

Also, for reducing the fixups, virtual entries like
STAC_927X_DELL_DMIC and STAC_D965_VERBS are introduced.
Signed-off-by: Takashi Iwai <tiwai@suse.de>