clk: samsung: exynos4: Add remaining suspend/resume handling

As of now, part of Exynos4 clock suspend/resume handling is located
in mach-exynos/pm.c, which is not where code accessing CMU registers
should reside.

This patch implements all the necessary suspend/resume handling code
in Exynos4 clock driver to allow dropping that old code.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Thomas Abraham <thomas.ab@samsung.com>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>