[ALSA] intel8x0 - Add support of 8 channel sound

Added the support of 8 channel sound for codecs that are known to work.
So far, only ALC850 is marked as a 8ch-support codec.

This fix is a modified version of the patch on ALSA BTS#2097 by
Martin Ellis:
	https://bugtrack.alsa-project.org/alsa-bug/view.php?id=2097

Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/ac97_codec.h

diff --git a/include/sound/ac97_codec.h b/include/sound/ac97_codec.h
index 0148058..049edc5 100644
--- a/include/sound/ac97_codec.h
+++ b/include/sound/ac97_codec.h
@@ -397,6 +397,7 @@
 #define AC97_HAS_NO_TONE	(1<<16) /* no Tone volume */
 #define AC97_HAS_NO_STD_PCM	(1<<17)	/* no standard AC97 PCM volume and mute */
 #define AC97_HAS_NO_AUX		(1<<18) /* no standard AC97 AUX volume and mute */
+#define AC97_HAS_8CH		(1<<19) /* supports 8-channel output */
 
 /* rates indexes */
 #define AC97_RATES_FRONT_DAC	0