ABI: sysfs-devices-power: document some RPM statistics

Changeset 8d4b9d1b ("PM / Runtime: Add runtime PM statistics (v3)")
added runtime_active_time and runtime_suspended_time, in order
to allow powertop to identify the amount of time a device is
active/suspended.

Add an ABI description for those.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/d5524b966d081c650121c4c496c2f7ab3df524e9.1632750608.git.mchehab+huawei@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-devices-power

@@ -269,3 +269,17 @@ Description:
 		the current runtime PM status of the device, which may be
 		"suspended", "suspending", "resuming", "active", "error" (fatal
 		error), or "unsupported" (runtime PM is disabled).
+
+What:		/sys/devices/.../power/runtime_active_time
+Date:		Jul 2010
+Contact:	Arjan van de Ven <arjan@linux.intel.com>
+Description:
+		Reports the total time that the device has been active.
+		Used for runtime PM statistics.
+
+What:		/sys/devices/.../power/runtime_suspended_time
+Date:		Jul 2010
+Contact:	Arjan van de Ven <arjan@linux.intel.com>
+Description:
+		Reports total time that the device has been suspended.
+		Used for runtime PM statistics.