ALSA: hda/realtek - Add the support of shared HP/Mic

A machine like Q1-ultra which has only a single HP but no mic-jack, we
can re-task the headhpone as an external mic jack.  This was done formerly
in ALC262 model=ultra quirk, and now the auto-parser supports this mode.

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