Without the "thinkpad" quirk, the dock mic in
Lenovo X220 tablet edition won't work.

BugLink: http://bugs.launchpad.net/bugs/751033
Cc: stable@kernel.org
Tested-by: NJames Ferguson <james.ferguson@canonical.com>
Signed-off-by: NDavid Henningsson <david.henningsson@canonical.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>