ALSA: hda - Remove non-working headphone control for Dell laptops

The previous commit re-enabled hp_nid setup for IDT92HD73*, but
it's unneeded indeed for Dell laptops that have multiple headphones.
Setting the extra hp_nid results in a non-working "Headpohne" mixer
control.  Thus hp_nid should be 0 for these dell models.

Also, the automatic addition of hp_nid should check whether it's
a dual-HP model or not.  For dual-HPs, the pins are already checked
by the early workaround.

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