arm/tegra: Make MACH_TEGRA_DT depend on ARCH_TEGRA_2x_SOC

Now that Tegra20 and Tegra30 device tree board files are separate,
MACH_TEGRA_DT (which enables the Tegra20 device tree board file) should
depend on Tegra20 support being enabled.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>
diff --git a/arch/arm/mach-tegra/Kconfig b/arch/arm/mach-tegra/Kconfig
index b3d78fc..373652d 100644
--- a/arch/arm/mach-tegra/Kconfig
+++ b/arch/arm/mach-tegra/Kconfig
@@ -66,6 +66,7 @@
 
 config MACH_TEGRA_DT
 	bool "Generic Tegra20 board (FDT support)"
+	depends on ARCH_TEGRA_2x_SOC
 	select USE_OF
 	help
 	  Support for generic NVIDIA Tegra20 boards using Flattened Device Tree