Documentation/ABI: add information about cpu_capacity

/sys/devices/system/cpu/cpu#/cpu_capacity describe information about
CPUs heterogeneity (ref. to Documentation/devicetree/bindings/arm/
cpu-capacity.txt).

Add such description.

Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 2a4a423..f3d5817 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -366,3 +366,10 @@
 Description:	AArch64 CPU registers
 		'identification' directory exposes the CPU ID registers for
 		 identifying model and revision of the CPU.
+
+What:		/sys/devices/system/cpu/cpu#/cpu_capacity
+Date:		December 2016
+Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>
+Description:	information about CPUs heterogeneity.
+
+		cpu_capacity: capacity of cpu#.