We found a Mic detection issue on many Lenovo laptops, those laptops
belong to differnt models and they have different audio design like
internal mic connects to the codec or PCH, they all have this problem,
the problem is if plugging a headset before powerup/reboot the
machine, after booting up, the headphone could be detected but Mic
couldn't. If we plug out and plug in the headset, both headphone and
Mic could be detected then.

Through debugging we found the codec on those laptops are same, it is
alc257, and if we don't disable the 3k pulldown in alc256_shutup(),
the issue will be fixed. So far there is no pop noise or power
consumption regression on those laptops after this change.

Cc: Kailang Yang <kailang@realtek.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Link: https://lore.kernel.org/r/20200914065118.19238-1-hui.wang@canonical.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>