Merge "aspeed devicetree for 4.7" from Joel Stanley:

This device trees for a pair of Aspeed BMC SoCs and the boards that
they sit in.

* tag 'aspeed-for-4.7-dts' of https://github.com/shenki/linux:
  arm/dst: Add Aspeed ast2500 device tree
  arm/dts: Add Aspeed ast2400 device tree
  doc/devicetree: Add Aspeed and Tyan to vendor-prefixes