clk: max77686: Refactor driver data handling

As a prerequisite for further patch adding OF clock provider support to
the driver, this patch changes the driver to store an array of struct
clk * as driver data.

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>