clk: samsung: exynos5433: mark PM functions as __maybe_unused

The suspend/resume functions are referenced conditionally, causing
a harmless warning when CONFIG_PM is disabled:

drivers/clk/samsung/clk-exynos5433.c:5476:12: error: 'exynos5433_cmu_resume' defined but not used [-Werror=unused-function]
drivers/clk/samsung/clk-exynos5433.c:5453:12: error: 'exynos5433_cmu_suspend' defined but not used [-Werror=unused-function]

This marks both as __maybe_unused to shut up the warning.

Fixes: 523d3de4 ("clk: samsung: exynos5433: Add support for runtime PM")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>