devicetree: bindings: Use linux-event-codes.h for evdev codes

Add a symlink to uapi/linux/linux-event-codes.h, and include that
instead of (re)defining all the evdev type and code values in
dt-bindings/input/input.h. This way we do not need to keep all the event
codes synced manually.

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>