clk: samsung: exynos3250: Add driver for CMU_ISP clock domain

clk: samsung: exynos3250: Add driver for CMU_ISP clock domain

Add clock controller for CMU ISP clock domain on Exynos3250,
providing clocks for FIMC-IS subsystem.

[b.michalska: use samsung_cmu_register_one to register
 the provider; updated DT binding documentation]

Signed-off-by: Tomasz Figa <[email protected]>
Signed-off-by: Chanwoo Choi <[email protected]>
Signed-off-by: Beata Michalska <[email protected]>
Acked-by: Kyungmin Park <[email protected]>
[s.nawrocki: added __init attribute which was missing in function
 exynos3250_cmu_platform_init() in function, which has been]
Reported-by: kbuild test robot <[email protected]>
Signed-off-by: Sylwester Nawrocki <[email protected]>
Signed-off-by: Michael Turquette <[email protected]>