These two machines have no mute LED string in BIOS.

BugLink: https://bugs.launchpad.net/bugs/1128934Tested-by: Tammy Yang <tammy.yang@canonical.com>
Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>