Instead of adding a special hook to trigger the mic-mute LED device,
call it always from the common callback function.  It won't hurt even
if no corresponding led cdev is present.

This is basically a preliminary change for the later patches to
convert the all mic-mute LED handling to LED class cdev.
Tested-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Link: https://lore.kernel.org/r/20200618110842.27238-2-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>