gpio: add flags to export GPIOs when requesting

Introduce new flags to automatically export GPIOs when using the convenience
functions gpio_request_one() or gpio_request_array(). This eases support for
custom boards where lots of GPIOs need to be exported for customer
applications.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index 620a078..e08a883 100644
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -322,6 +322,9 @@
 	* GPIOF_OPEN_DRAIN	- gpio pin is open drain type.
 	* GPIOF_OPEN_SOURCE	- gpio pin is open source type.
 
+	* GPIOF_EXPORT_DIR_FIXED	- export gpio to sysfs, keep direction
+	* GPIOF_EXPORT_DIR_CHANGEABLE	- also export, allow changing direction
+
 since GPIOF_INIT_* are only valid when configured as output, so group valid
 combinations as: