ARM: dts: omap3: add missing unit name to PMU node

This patch fixes the following DTC warnings:

"pmu has a reg or ranges property, but no unit name"
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/omap3.dtsi

@@ -43,7 +43,7 @@ cpu@0 {
 		};
 	};
 
-	pmu {
+	pmu@54000000 {
 		compatible = "arm,cortex-a8-pmu";
 		reg = <0x54000000 0x800000>;
 		interrupts = <3>;