drivers/bus: Move Arm CCN PMU driver

The arm-ccn driver is purely a perf driver for the CCN PMU, not a bus
driver in the sense of the other residents of drivers/bus/, so let's
move it to the appropriate place for SoC PMU drivers. Not to mention
moving the documentation accordingly as well.

Acked-by: Pawel Moll <pawel.moll@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Documentation/devicetree/bindings/perf/arm-ccn.txt

@@ -0,0 +1,22 @@
+* ARM CCN (Cache Coherent Network)
+
+Required properties:
+
+- compatible: (standard compatible string) should be one of:
+	"arm,ccn-502"
+	"arm,ccn-504"
+	"arm,ccn-508"
+
+- reg: (standard registers property) physical address and size
+	(16MB) of the configuration registers block
+
+- interrupts: (standard interrupt property) single interrupt
+	generated by the control block
+
+Example:
+
+	ccn@2000000000 {
+		compatible = "arm,ccn-504";
+		reg = <0x20 0x00000000 0 0x1000000>;
+		interrupts = <0 181 4>;
+	};