[PATCH for 3.10] Misc small improvements to Kirkwood-based OpenBlocks A6 platform

[Thomas Petazzoni]

Jason, Andrew, Greg,

Here is a set of 3 patches making small improvements to the support of
the Kirkwood-based PlatHome OpenBlocks A6 platform.

The first two patches clean up the pinctrl definitions in the board
Device Tree.

The third patch adds the support for a GPIO-connected button.

Thanks,

Thomas