ASUS Zenbook UX31A has yet another problem -- softer output level than
others.  According to the measurement, the peak output difference
between 31A and 31E is 5dB.  As ALC269VB has a COEF for the class-D
pre-amp, let's apply it for +5dB.
Signed-off-by: Takashi Iwai <tiwai@suse.de>