Add input-event-codes header file and move all type and axis defines
there.

The purpose of this new header file is to have a single canonical source
for event-codes which can be used outside of C-code too. One example of
such usage is the use of event-codes in devicetree source files.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>