Input: i8042 - disable mux on Toshiba C850D

On Toshiba Satellite C850D, the touchpad and the keyboard might randomly
not work at boot. Preventing MUX mode activation solves this issue.

Signed-off-by: Anisse Astier <anisse@astier.eu>
Cc: stable@kernel.org
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>