dt-bindings: input: allwinner,sun4i-a10-lrad: drop redundant type from label

dtschema defines label as string, so $ref in other bindings is
redundant.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20240226122934.89257-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>