ALSA: hda - Move mic mute LED helper to the generic parser

Move the code for setting up and controlling the mic mute LED hook
from dell-wmi helper to the generic parser, so that it can be referred
from the multiple driver codes.

No functional change.

Tested-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>