ALSA: hda - Clear left-over hp_pins in snd_hda_parse_pin_def_config()

In snd_hda_parse_def_config(), some unused values may remain in hp_pins[]
array during the headphone-reassignment workaround.  This patch clears
the unused array members.

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