ALSA: hda: intel-nhlt: handle NHLT VENDOR_DEFINED DMIC geometry

The NHLT spec defines a VENDOR_DEFINED geometry, which requires
reading additional information to figure out the number of
microphones.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>