ARM: BCM53573: Specify PMU and its ILP clock in the DT

ILP clock (sometimes called a "slow clock") is a part of PMU (Power
Management Unit). There has been recently added a driver for it, so add
a proper entry in the DT as well.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

arch/arm/boot/dts/bcm53573.dtsi

@@ -143,5 +143,17 @@ gmac0: ethernet@5000 {
 		gmac1: ethernet@b000 {
 			reg = <0xb000 0x1000>;
 		};
+
+		pmu@12000 {
+			compatible = "simple-mfd", "syscon";
+			reg = <0x00012000 0x00001000>;
+
+			ilp: ilp {
+				compatible = "brcm,bcm53573-ilp";
+				clocks = <&alp>;
+				#clock-cells = <0>;
+				clock-output-names = "ilp";
+			};
+		};
 	};
 };