ALSA: hda - Add quirk for ASUS G751 laptop

ASUS G751 requires the extra COEF initialization to make it microphone
working properly.

Reported-and-tested-by: Håvard <hovardslill@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>