ARM: EXYNOS: Fix potential NULL pointer access in exynos_sys_powerdown_conf

If no platform devices binded to the driver but driver itself loaded and
exynos_sys_powerdown_conf is called from
arch/arm/mach-exynos/{suspend.c, pm.c} it will result in NULL pointer access,
to prevent this added check on pmu_context for NULL.

Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Tested-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>

arch/arm/mach-exynos/pmu.c

@@ -748,8 +748,12 @@ static void exynos5_powerdown_conf(enum sys_powerdown mode)
 void exynos_sys_powerdown_conf(enum sys_powerdown mode)
 {
 	unsigned int i;
+	const struct exynos_pmu_data *pmu_data;
+
+	if (!pmu_context)
+		return;
 
-	const struct exynos_pmu_data *pmu_data = pmu_context->pmu_data;
+	pmu_data = pmu_context->pmu_data;
 
 	if (pmu_data->powerdown_conf)
 		pmu_data->powerdown_conf(mode);