ALSA: hda/realtek - Use a common helper for hp pin reference

Replace the open-codes in many places with a new common helper for
performing the same thing: referring to the primary headphone pin.

This eventually fixes the potentially missing headphone pin on some
weird devices, too.

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>