clk: samsung: exynos5420: Use generic helper for handling suspend/resume

Replace common suspend/resume handling code by generic helper.
Almost no functional change, the only difference is in handling
of hypothetical memory allocation failure on boot.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sylwester Nawrocki <snawrocki@kernel.org>