[ALSA] hda-codec - Fix 8-channel auto-configuration

Fix the auto-configuration of 8-channel devices.  The sequence numbers
of usual 7.1 outputs are: 0/1/2/4 = Front/CLFE/Rear/Side

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>