Documentation: ABI: make current_governer_ro as a candidate for removal

Since both current_governor and current_governor_ro co-exist under
/sys/devices/system/cpu/cpuidle/ file, and it's duplicate,
make current_governer_ro as a candidate for removal.
Signed-off-by: Hanjun Guo <guohanjun@huawei.com>
Reviewed-by: Doug Smythies <dsmythies@telus.net>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/ABI/obsolete/sysfs-cpuidle

+What:		/sys/devices/system/cpu/cpuidle/current_governor_ro
+Date:		April, 2020
+Contact:	linux-pm@vger.kernel.org
+Description:
+	current_governor_ro shows current using cpuidle governor, but read only.
+	with the update that cpuidle governor can be changed at runtime in default,
+	both current_governor and current_governor_ro co-exist under
+	/sys/devices/system/cpu/cpuidle/ file, it's duplicate so make
+	current_governor_ro obselete.