The compatible string for Rockchip RK3288 is wrongly provided in the
'enum' item, in addition to the subsequent 'const', which allows the
usage of an incorrect specification:

  compatible = "rockchip,rk3288-timer", "rockchip,rk3288-timer";

As the rk3288 string is also specified in the top-most 'const' item, the
binding already allows the usage of the correct variant:

  compatible = "rockchip,rk3288-timer";

Drop the unwanted rk3288 entry from the enum.

Fixes: faa186ad ("dt-bindings: timer: convert rockchip,rk-timer.txt to YAML")
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20230419181309.338354-2-cristian.ciocaltea@collabora.com