ARM: dts: Add clock provider specific properties to max77686 node

This patch adds a label and #clock-cells property to device node of
max77686 PMIC to allow using it as a clock provider.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>