asus-wmi: Enable autorepeat for hotkey input device

The T101MT Home/Express Gate key autorepeats in hardware, but
sparse-keymap does not support hardware autorepeat. Enable the
input core's software autorepeat to emulate the hardware behavior.
Normal hotkeys are autoreleased, so the behavior of these keys
will not be affected.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Corentin Chary <corentin.chary@gmail.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>