Documentation: gpio: Move drivers-on-gpio.txt to driver-api

Move gpio/drivers-on-gpio.txt to driver-api/gpio/drivers-on-gpio.rst and
make sure it builds cleanly as ReST.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/Documentation/gpio/sysfs.txt b/Documentation/gpio/sysfs.txt
index 6cdeab8..58eeab8 100644
--- a/Documentation/gpio/sysfs.txt
+++ b/Documentation/gpio/sysfs.txt
@@ -32,9 +32,8 @@
 GPIO drivers could be all that the system really needs.
 
 DO NOT ABUSE SYSFS TO CONTROL HARDWARE THAT HAS PROPER KERNEL DRIVERS.
-PLEASE READ THE DOCUMENT NAMED "drivers-on-gpio.txt" IN THIS DOCUMENTATION
-DIRECTORY TO AVOID REINVENTING KERNEL WHEELS IN USERSPACE. I MEAN IT.
-REALLY.
+PLEASE READ THE DOCUMENT AT Documentation/driver-api/gpio/drivers-on-gpio.rst
+TO AVOID REINVENTING KERNEL WHEELS IN USERSPACE. I MEAN IT. REALLY.
 
 Paths in Sysfs
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