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>
diff --git a/drivers/perf/Makefile b/drivers/perf/Makefile
index c2f2741..5004abe 100644
--- a/drivers/perf/Makefile
+++ b/drivers/perf/Makefile
@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_ARM_CCN) += arm-ccn.o
 obj-$(CONFIG_ARM_DSU_PMU) += arm_dsu_pmu.o
 obj-$(CONFIG_ARM_PMU) += arm_pmu.o arm_pmu_platform.o
 obj-$(CONFIG_ARM_PMU_ACPI) += arm_pmu_acpi.o