ARM: dts: correct memory size for exynos4412-odroidx

Last megabyte of RAM is used by secure firmware and should not be accessed
by Linux kernel, so correct available memory size in DTS file.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

arch/arm/boot/dts/exynos4412-odroidx.dts

@@ -19,7 +19,7 @@ / {
 	compatible = "hardkernel,odroid-x", "samsung,exynos4412", "samsung,exynos4";
 
 	memory {
-		reg = <0x40000000 0x40000000>;
+		reg = <0x40000000 0x3FF00000>;
 	};
 
 	firmware@0204F000 {