media: dt-bindings: rc: add rc-beelink-mxiii

Add a binding for the rc-beelink-mxiii remote keymap

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>