GPIO unexport fix #1
Description
I found that unexporting GPIOs did not work, i.e. after exporting and unexporting a pin it can not be exported again. Therefore you could for example only use avrdude once after each boot.
This is a bug in the kernel GPIO driver for the SoC. There was also a bug report in the OpenWRT Trac, and I attached a patch that seems to solve the problem there. https://dev.openwrt.org/ticket/14309
Probably it would be a good idea to add this somehow the WRTnode default images, as probably a lot of people want to play with its GPIOs. But I do not know how :)