ALSA: hda/realtek: Enable front panel headset LED on Lenovo ThinkStation P520

ALSA: hda/realtek: Enable front panel headset LED on Lenovo ThinkStation P520

On Lenovo P520, the front panel headset LED isn't lit up right now.

Realtek states that the LED needs to be enabled by ALC233's GPIO2, so
let's do it accordingly to light the LED up.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Acked-by: Hui Wang <hui.wang@canonical.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200914070231.13192-1-kai.heng.feng@canonical.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>