ARM: exynos: introduce EXYNOS_ATAGS symbol

As a preparation for multiplatform support, this introduces
a new Kconfig symbol to split the ATAGS based EXYNOS platforms
from the DT based ones. Turning off CONFIG_EXYNOS_ATAGS disables
all platforms that are not yet converted to DT, and we can
have code that relies on DT checking for this symbol being
disabled.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/mach-exynos/Kconfig

@@ -85,6 +85,19 @@ config EXYNOS4_MCT
 	help
 	  Use MCT (Multi Core Timer) as kernel timers
 
+config EXYNOS_ATAGS
+	bool "ATAGS based boot for EXYNOS (deprecated)"
+	depends on !ARCH_MULTIPLATFORM
+	depends on ATAGS
+	default y
+	help
+	  The EXYNOS platform is moving towards being completely probed
+	  through device tree. This enables support for board files using
+	  the traditional ATAGS boot format.
+	  Note that this option is not available for multiplatform builds.
+
+if EXYNOS_ATAGS
+
 config EXYNOS_DEV_DMA
 	bool
 	help
@@ -400,6 +413,8 @@ config MACH_SMDK4412
 	  Machine support for Samsung SMDK4412
 endif
 
+endif
+
 comment "Flattened Device Tree based board for EXYNOS SoCs"
 
 config MACH_EXYNOS4_DT