ALSA: hda/realtek - Fix unused variable warning

The previous fix forgot to remove the unused variable that triggers a
compile warning now:
  sound/pci/hda/patch_realtek.c: In function 'alc285_fixup_hp_gpio_led':
  sound/pci/hda/patch_realtek.c:4163:19: warning: unused variable 'spec' [-Wunused-variable]

Fix it.

Fixes: 40469064

 ("ALSA: hda - reverse the setting value in the micmute_led_set")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Link: https://lore.kernel.org/r/20200812070256.32145-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>