ARM: EXYNOS: Make local function static

Function is not used outside of this unit, make it static.
Signed-off-by: NKrzysztof Kozlowski <k.kozlowski.k@gmail.com>
Signed-off-by: NKukjin Kim <kgene@kernel.org>

arch/arm/mach-exynos/pmu.c

@@ -698,7 +698,7 @@ static void exynos_power_off(void)
 		;
 }
 
-void exynos5420_powerdown_conf(enum sys_powerdown mode)
+static void exynos5420_powerdown_conf(enum sys_powerdown mode)
 {
 	u32 this_cluster;