ALSA: hda: Use mb31 quirk for an iMac model

BugLink: https://launchpad.net/bugs/542550
Symptom: On the reporter's iMac, in Ubuntu 10.04 LTS neither playback
nor capture appear audible out-of-the-box.

Test case: Boot from an Ubuntu 10.04 LTS live cd or from an installed
configuration and attempt to play or capture audio.

Resolution: Specify the mb31 quirk for this machine in the codec SSID
table.

Reported-and-Tested-By: f3a97
Cc: <stable@kernel.org>
Signed-off-by: Daniel T Chen <crimsun@ubuntu.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>