dt-bindings: soc: ti: pruss: Update IEP node bindings

IEP driver needs to know the clock rate of the IEP
core clock. Provide a clocks property for that.

TODO: Update the existing examples once these clocks are
added on those SoCs

Signed-off-by: Roger Quadros <rogerq@ti.com>
[s-anna@ti.com: add under the proper sub-section]
Signed-off-by: Suman Anna <s-anna@ti.com>

Documentation/devicetree/bindings/soc/ti/ti,pruss.txt

@@ -138,6 +138,11 @@ are applicable only for K3 SoCs. They are represented as follows:
 See Documentation/devicetree/bindings/mfd/syscon.txt for generic syscon
 binding details.
 
+Required Properties:
+--------------------
+The following are required properties for IEP nodes
+- clocks        : phandle to IEP core clock.
+
 
 IEPCLK MUX Clock node
 =====================