ALSA: hda/realtek - Add headset mode support for Dell laptop

This platform was only one phone Jack.
Add dummy lineout verb to fix automute mode disable.
This just the workaround.

[ More background information:
  since the platform has only a headphone jack without speaker, the
  driver doesn't create the auto-mute control.  Meanwhile we do update
  the headset mode via the automute hook in the driver, thus with this
  setup, the headset won't be updated any longer.

  By adding a dummy line-out pin here, the auto-mute is added by the
  driver, and the headset update is triggered properly.

  Note that this is different from the other
  ALC274_FIXUP_DELL_AIO_LINEOUT_VERB, which has the real line-out pin,
  while this quirk adds a dummy line-out pin.  -- tiwai ]

Signed-off-by: Kailang Yang <kailang@realtek.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>