coresight: binding for ETMv4 coresight drivers

Adding compatible string for new coresight ETMv4 tracer.
Signed-off-by: NMathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/arm/coresight.txt

@@ -17,6 +17,7 @@ its hardware characteristcs.
 		- "arm,coresight-tmc", "arm,primecell";
 		- "arm,coresight-funnel", "arm,primecell";
 		- "arm,coresight-etm3x", "arm,primecell";
+		- "arm,coresight-etm4x", "arm,primecell";
 		- "qcom,coresight-replicator1x", "arm,primecell";
 
 	* reg: physical base address and length of the register