Input: i8042 - add ThinkPad S230u to i8042 nomux list

On the Lenovo ThinkPad Twist S230u (3347-4HU) with BIOS version
"GDETC1WW (1.81 ) 06/27/2019", whether booted in UEFI or Legacy/CSM mode
the keyboard, Synaptics TouchPad, and TrackPoint either do not function
or stop functioning a few minutes after boot.  This problem has been
noted before, perhaps only occurring on BIOS 1.57 and
later.[1][2][3][4][5]

This model does not have an external PS/2 port, so mux does not appear
to be useful.

Odds of a BIOS fix appear to be low: 1.57 was released over 6 years ago
and although the [BIOS changelog] notes "Fixed an issue of UEFI
touchpad/trackpoint/keyboard/touchscreen" in 1.58, it appears to be
insufficient.

Adding 33474HU to the nomux list avoids the issue on my system.

[1]: https://bugs.launchpad.net/bugs/1210748
[2]: https://bbs.archlinux.org/viewtopic.php?pid=1360425
[3]: https://forums.linuxmint.com/viewtopic.php?f=46&t=41200
[4]: https://forums.linuxmint.com/viewtopic.php?f=49&t=157115
[5]: https://forums.lenovo.com/topic/findpost/27/1337119
[BIOS changelog]: https://download.lenovo.com/pccbbs/mobiles/gduj33uc.txt

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/feb8a8339a67025dab3850e6377eb6f3a0e782ba.1587400635.git.kevin@kevinlocke.name
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>