ARM: EXYNOS: Migrate clock support to common clock framework

Remove Samsung specific clock support in Exynos4/5 and migrate to
use common clock framework.

Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Tested-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Tested-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>