ARM: dts: AM33xx: Add RNG node

Add the AM33xx RNG module's device tree data.
Also add Documentation file describing the data
for the RNG module.
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

Documentation/devicetree/bindings/hwrng/omap_rng.txt

+OMAP SoC HWRNG Module
+
+Required properties:
+
+- compatible : Should contain entries for this and backward compatible
+  RNG versions:
+  - "ti,omap2-rng" for OMAP2.
+  - "ti,omap4-rng" for OMAP4, OMAP5 and AM33XX.
+  Note that these two versions are incompatible.
+- ti,hwmods: Name of the hwmod associated with the RNG module
+- reg : Offset and length of the register set for the module
+- interrupts : the interrupt number for the RNG module.
+		Only used for "ti,omap4-rng".
+
+Example:
+/* AM335x */
+rng: rng@48310000 {
+	compatible = "ti,omap4-rng";
+	ti,hwmods = "rng";
+	reg = <0x48310000 0x2000>;
+	interrupts = <111>;
+};

arch/arm/boot/dts/am33xx.dtsi

@@ -779,5 +779,12 @@ mcasp1: mcasp@4803C000 {
 				<&edma 11>;
 			dma-names = "tx", "rx";
 		};
+
+		rng: rng@48310000 {
+			compatible = "ti,omap4-rng";
+			ti,hwmods = "rng";
+			reg = <0x48310000 0x2000>;
+			interrupts = <111>;
+		};
 	};
 };