ARM: dt: tegra: harmony: configure power off

Add DT property to tell the TPS6586x that it should provide the
pm_power_off() implementation. This allows "shutdown" to work.
Signed-off-by: Stephen Warren <swarren@nvidia.com>

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

@@ -281,6 +281,8 @@ pmic: tps6586x@34 {
 			reg = <0x34>;
 			interrupts = <0 86 0x4>;
 
+			ti,system-power-controller;
+
 			#gpio-cells = <2>;
 			gpio-controller;