regulator: update a filename in documentation

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: Liam Girdwood <lrg@slimlogic.co.uk>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>

Documentation/power/regulator/overview.txt

@@ -168,4 +168,4 @@ relevant to non SoC devices and is split into the following four interfaces:-
       userspace via sysfs. This could be used to help monitor device power
       consumption and status.
 
-        See Documentation/ABI/testing/regulator-sysfs.txt
+        See Documentation/ABI/testing/sysfs-class-regulator