ALSA: HDA: Add auto-mute for Thinkpad SL410/SL510

BugLink: http://launchpad.net/bugs/580006



SKU turns off auto-mute for these machines, so ignore the SKU.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>