ALSA: hda - Fix headphone pin config for Lifebook T731

Some BIOS version of Fujitsu Lifebook T731 seems to set up the
headphone pin (0x21) without the assoc number 0x0f while it's set only
to the output on the docking port (0x1a).  With the recent commit
[03ad6a8c: ALSA: hda - Fix "PCM" name being used on one DAC when
 there are two DACs], this resulted in the weird mixer element
mapping where the headphone on the laptop is assigned as a shared
volume with the speaker and the docking port is assigned as an
individual headphone.

This patch improves the situation by correcting the headphone pin
config to the more appropriate value.

Reported-and-tested-by: Taylor Smock <smocktaylor@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>