clk: samsung: mark s3c...._clk_sleep_init() as __init

These functions are referencing s3c...._clk_regs[], which are marked as
__initdata. When compiling with CONFIG_DEBUG_SECTION_MISMATCH=y, this
produces warnings like

WARNING: vmlinux.o(.text+0x198350):
Section mismatch in reference from the function s3c2410_clk_sleep_init()
to the (unknown reference) .init.data:(unknown)

Mark the s3c...._clk_sleep_init() functions as __init in
order to fix this.

Fixes: ca2e90ac

 ("clk: samsung: add clock controller driver for s3c2412")
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>