[ALSA] ice1712 - Disable AC97 for DMX6fire

Consumer AC97 is not used by the Terratec DMX6fire, but eeprom bit indicates
it is; change the stored value to disable failing consumer mode.

Signed-off-by: Alan Horstmann <gineera@aspect135.co.uk>
Signed-off-by: Takashi Iwai <tiwai@suse.de>