ARM: dt: tegra30: Rename "smmu" to "iommu"

Use functional name for DT entry instead of h/w name.
Signed-off-by: NHiroshi Doyu <hdoyu@nvidia.com>
Signed-off-by: NStephen Warren <swarren@nvidia.com>

arch/arm/boot/dts/tegra30.dtsi

@@ -440,7 +440,7 @@
 		interrupts = <0 77 0x04>;
 	};
 
-	smmu {
+	iommu {
 		compatible = "nvidia,tegra30-smmu";
 		reg = <0x7000f010 0x02c
 		       0x7000f1f0 0x010