ALSA: hda/realtek - Enable the headset-mic on a Xiaomi's laptop

The headset on this machine is not defined, after applying the quirk
ALC256_FIXUP_ASUS_HEADSET_MIC, the headset-mic works well

BugLink: https://bugs.launchpad.net/bugs/1846148


Cc: <stable@vger.kernel.org>
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Link: https://lore.kernel.org/r/20191121025427.8856-1-hui.wang@canonical.com


Signed-off-by: Takashi Iwai <tiwai@suse.de>