ALSA: HDA: Add dock mic quirk for Lenovo Thinkpad X220

This quirk is needed for the docking station mic of
Lenovo Thinkpad X220 to function correctly.

BugLink: http://bugs.launchpad.net/bugs/746259
Cc: stable@kernel.org
Tested-by: James Ferguson <james.ferguson@canonical.com>
Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>