ALSA: hda - Add HP ZBook 15u G3 Conexant CX20724 GPIO mute leds

The HP ZBook 15u G3 has a Conexant CX20724 with mute led on GPIO1 and
mic mute led on GPIO2.
Adding CXT_FIXUP_MUTE_LED_GPIO inspired on patch_realtek's one.

Signed-off-by: Jerónimo Borque <jeronimo@borque.com.ar>
Signed-off-by: Takashi Iwai <tiwai@suse.de>