Input: atkbd - document "no new force-release quirks" policy

To save people some time let's document that we do not want new quirks for
"force-release" keys in the kernel and that they should patch userspace
(udev) instead.

Suggested-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>