ALSA: hda - Add missing ALC680_* definitions

Also update the documentation.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/Documentation/sound/alsa/HD-Audio-Models.txt b/Documentation/sound/alsa/HD-Audio-Models.txt
index 84e81ad..03771d7 100644
--- a/Documentation/sound/alsa/HD-Audio-Models.txt
+++ b/Documentation/sound/alsa/HD-Audio-Models.txt
@@ -114,6 +114,11 @@
   samsung-nc10	Samsung NC10 mini notebook
   auto		auto-config reading BIOS (default)
 
+ALC680
+======
+  base		Base model (ASUS NX90)
+  auto		auto-config reading BIOS (default)
+
 ALC882/883/885/888/889
 ======================
   3stack-dig	3-jack with SPDIF I/O