clk/exynos4: Fix compilation warning

Fixes the following warning:
WARNING: drivers/built-in.o(.text.unlikely+0x2c50): Section mismatch in reference from the function exynos4_clk_sleep_init() to the (unknown reference) .init.data:(unknown)
   The function exynos4_clk_sleep_init() references
   the (unknown reference) __initdata (unknown).
   This is often because exynos4_clk_sleep_init lacks a __initdata
   annotation or the annotation of (unknown) is wrong.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>