clk: max77686: Add DT include for MAX77686 PMIC clock

This patch adds a dt-binding include for Maxim 77686
PMIC clock IDs that can be used by both the max77686
clock driver and Device Tree source files.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>