[ALSA] hda-codec - Add support of ALC268 codec

Added the support of new ALC268 codec chip.

Signed-off-by: Kailang Yang <kailang@realtek.com.tw>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>