dt-bindings: timer: rockchip: Drop superfluous rk3288 compatible

dt-bindings: timer: rockchip: Drop superfluous rk3288 compatible

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: faa186adbd06 ("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