dt-bindings: input: Increase maximum keycode value to 0x2ff

The maximum keycode value for Linux is 0x2ff, not 0xff. There's already
users and examples with values greater than 0xff, but the schema is not
yet applied in those cases.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Jeff LaBundy <jeff@labundy.com>
Link: https://lore.kernel.org/r/20220608211207.2058487-2-robh@kernel.org


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>