ARM: dt: tegra: configure power off for some boards

For Seaboard, Ventana, and Cardhu, add DT property to tell the regulator
that it should provide the pm_power_off() implementation. This allows
"shutdown" to work.
Signed-off-by: NStephen Warren <swarren@nvidia.com>

arch/arm/boot/dts/tegra20-seaboard.dts

@@ -379,6 +379,8 @@
 			reg = <0x34>;
 			interrupts = <0 86 0x4>;
 
+			ti,system-power-controller;
+
 			#gpio-cells = <2>;
 			gpio-controller;
 

arch/arm/boot/dts/tegra20-ventana.dts

@@ -295,6 +295,8 @@
 			reg = <0x34>;
 			interrupts = <0 86 0x4>;
 
+			ti,system-power-controller;
+
 			#gpio-cells = <2>;
 			gpio-controller;
 

arch/arm/boot/dts/tegra30-cardhu.dtsi

@@ -156,6 +156,8 @@
 			#interrupt-cells = <2>;
 			interrupt-controller;
 
+			ti,system-power-controller;
+
 			#gpio-cells = <2>;
 			gpio-controller;