Force to choose model=ref for some Dell laptops with STAC9200 codec
chip for fixing the silent mic recording problem (possibly due to
a BIOS bug).  Reference: ALSA bug#2038
So far, applied to Inspiron 630m, Latitude D620 and 120L.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>