Documentation/ABI: sysfs-platform-ideapad-laptop: conservation_mode attribute

Document the conservation_mode attributes provided by the ideapad-laptop module.

Fixes: ade50296186a ("platform/x86: ideapad-laptop: Expose conservation mode switch")
Signed-off-by: Barnabás Pőcze <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Hans de Goede <[e-mail]>
Signed-off-by: Hans de Goede <[e-mail]>

Documentation/ABI/testing/sysfs-platform-ideapad-laptop

···
 			* 1 -> Switched On
 			* 0 -> Switched Off
 
+What:		/sys/bus/platform/devices/VPC2004:*/conservation_mode
+Date:		Aug 2017
+KernelVersion:	4.14
+Contact:	[e-mail]
+Description:
+		Controls whether the conservation mode is enabled or not.
+		This feature limits the maximum battery charge percentage to
+		around 50-60% in order to prolong the lifetime of the battery.
+
 What:		/sys/bus/platform/devices/VPC2004:*/fn_lock
 Date:		May 2018
 KernelVersion:	4.18