clk: samsung: Add a separate driver for Exynos4412 ISP clocks

Some registers for the Exynos 4412 ISP (Camera subsystem) clocks are
located in the ISP power domain. Because those registers are also
located in a different memory region than the main clock controller,
support for them can be provided by a separate clock controller.
This in turn allows to almost seamlessly make it aware of the power
domain using recently introduced runtime PM support for clocks.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>