dt-bindings: pinctrl: nuvoton,npcm845: Drop redundant type for "slew-rate"

pincfg-node.yaml already defines the type for "slew-rate", so drop the
type from the nuvoton,npcm845-pinctrl binding.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240124190106.1540585-2-robh@kernel.org


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>