ALSA: hda - add mic mute led hook for dell machines

The mic mute led on dell laptops is controlled by the wmi driver.
Followed this part being merged to the kernel, we add the mic mute led
hook in the hda driver.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>