clk: max77686: Convert to the generic max clock driver

Clocks drivers for Maxim PMIC are very similar so they can
be converted to use the generic Maxim clock driver.

Also, while being there use module_platform_driver() helper
macro to eliminate more boilerplate code.

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