ALSA: hda - use dell_micmute_led_set() instead of dell_app_wmi_led_set()

The dell_app_wmi_led_set() method introduced in commit db6d8cc0
("dell-led: add mic mute led interface") was implemented as an easily
extensible entry point for other modules to set the state of various
LEDs.  However, almost three years later it is still only used to
control the mic mute LED, so it will be replaced with direct calls to
dell_micmute_led_set().

Signed-off-by: Michał Kępień <kernel@kempniu.pl>
Tested-by: Alex Hung <alex.hung@canonical.com>
Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>