ALSA: hda - Fix silent HP output on D975

Some desktops seems to have no HP/mic jack detection on the front panel,
which results in the silent output in the recent driver, because the
driver mutes the output (to save power) when no plug is detected.

This patch adds a new model that disables the jack-detection.

Signed-off-by: Takashi Iwai <tiwai@suse.de>