The workaround to force VREF50 for dallas/hp model with ALC861VD
was introduced in commit 8fdcb6fe,
but it contained wrong pincap override bits.

This patch fixes to exclude VREF80 pincap bit correctly.

Cc: <stable@vger.kernel.org> [v3.2+]
Signed-off-by: Takashi Iwai <tiwai@suse.de>