dt-bindings: omap-rng: Document SafeXcel IP-76 device variant

This commits add missing fields in the documentation that are used
by the new device variant. It also includes DT example to show how
the variant should be used.
Signed-off-by: Romain Perier <romain.perier@free-electrons.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Documentation/devicetree/bindings/rng/omap_rng.txt

-OMAP SoC HWRNG Module
+OMAP SoC and Inside-Secure HWRNG Module
 
 Required properties:
 
@@ -6,11 +6,13 @@ Required properties:
   RNG versions:
   - "ti,omap2-rng" for OMAP2.
   - "ti,omap4-rng" for OMAP4, OMAP5 and AM33XX.
+  - "inside-secure,safexcel-eip76" for SoCs with EIP76 IP block
   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".
+		Used for "ti,omap4-rng" and "inside-secure,safexcel-eip76"
+- clocks: the trng clock source
 
 Example:
 /* AM335x */
@@ -20,3 +22,11 @@ rng: rng@48310000 {
 	reg = <0x48310000 0x2000>;
 	interrupts = <111>;
 };
+
+/* SafeXcel IP-76 */
+trng: rng@f2760000 {
+	compatible = "inside-secure,safexcel-eip76";
+	reg = <0xf2760000 0x7d>;
+	interrupts = <GIC_SPI 59 IRQ_TYPE_LEVEL_HIGH>;
+	clocks = <&cpm_syscon0 1 25>;
+};