ARM: 6976/1: pmu: add OF probing support

This is based on an earlier patch from Rob Herring <rob.herring@calxeda.com>

> Add OF match table to enable OF style driver binding. The dts entry is like
> this:
>
> pmu {
> 	compatible = "arm,cortex-a9-pmu";
> 	interrupts = <100 101>;
> };
>
> The use of pdev->id as an index breaks with OF device binding, so set the type
> based on the OF compatible string.

This modification sets the PMU hardware type based on data embedded in the
binding, allowing easy addition of new PMU types in future.

Support for new PMU types not provided by devicetree can be added later using
platform_device_id tables in a similar fashion.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Jamie Iles <jamie@jamieiles.com>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

Documentation/devicetree/bindings/arm/pmu.txt

@@ -0,0 +1,21 @@
+* ARM Performance Monitor Units
+
+ARM cores often have a PMU for counting cpu and cache events like cache misses
+and hits. The interface to the PMU is part of the ARM ARM. The ARM PMU
+representation in the device tree should be done as under:-
+
+Required properties:
+
+- compatible : should be one of
+	"arm,cortex-a9-pmu"
+	"arm,cortex-a8-pmu"
+	"arm,arm1176-pmu"
+	"arm,arm1136-pmu"
+- interrupts : 1 combined interrupt or 1 per core.
+
+Example:
+
+pmu {
+        compatible = "arm,cortex-a9-pmu";
+        interrupts = <100 101>;
+};