dt-binding: clk: npcm845: Add binding for Nuvoton NPCM8XX Clock

Add binding for the Arbel BMC NPCM8XX Clock controller.

Signed-off-by: Tomer Maimon <tmaimon77@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>