ARM: SoC changes, part 2

This is the second part of the general SoC updates, containing
everything that did not make it in the initial pull request,
or that came in as a bugfix later.

 - Devicetree updates for SoCFPGA, ASPEED, AT91 and Rockchip, including
   a new machine using an ASPEED BMC.

 - More DT fixes from Krzysztof Kozlowski across platforms

 - A new SoC platform for the GXP baseboard management controller,
   used in current server products from HPE.