Move reg_save[] into CONFIG_PM_SLEEP dependency block as it is used only
by suspend and resume functions.

This fixes the warning on CONFIG_PM_SLEEP=n:
drivers/clk/samsung/clk-exynos-audss.c:29:22: warning: ‘reg_save’ defined but not used [-Wunused-variable]
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Tomasz Figa <t.figa@samsung.com>