ARM: EXYNOS: Fix Kconfig dependencies for device tree enabled machine files

Add config dependency for Exynos4 and Exynos5 device tree enabled machine
files on config options ARCH_EXYNOS4 and ARCH_EXYNOS5 respectively.
Enabling machine support without proper ARCH support enabled is incorrect.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

arch/arm/mach-exynos/Kconfig

@@ -368,6 +368,7 @@ comment "Flattened Device Tree based board for EXYNOS SoCs"
 
 config MACH_EXYNOS4_DT
 	bool "Samsung Exynos4 Machine using device tree"
+	depends on ARCH_EXYNOS4
 	select CPU_EXYNOS4210
 	select USE_OF
 	select ARM_AMBA
@@ -380,6 +381,7 @@ config MACH_EXYNOS4_DT
 
 config MACH_EXYNOS5_DT
 	bool "SAMSUNG EXYNOS5 Machine using device tree"
+	depends on ARCH_EXYNOS5
 	select SOC_EXYNOS5250
 	select USE_OF
 	select ARM_AMBA