Add a model/fixup string "lenovo-dock", for Thinkpad T430s, to allow
sound in docking station.

Tested on Lenovo T430s with ThinkPad Mini Dock Plus Series 3

Cc: stable@kernel.org
Signed-off-by: Philipp A. Mohrenweiser <phiamo@googlemail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>