ALSA: hda: Added Realtek ALC888 model entry for Acer Aspire 4930G laptop

Added Realtek ALC888 model entry for the Acer Aspire 4930G laptop that
fixes the following features:
- internal microphone
- heaphone jack sense
- channel mode

Signed-off-by: Vincent Petry <PVince81@yahoo.fr>
Signed-off-by: Takashi Iwai <tiwai@suse.de>