Merge "ARM: mediatek: arm64 changes for v3.20" from Matthias Brugger:

Add support for mt8173 SoC from Mediatek.

- add DT bindings documentation
- add dts files for SoC and evaluation board
- add to Kconfig and defconfig

* tag 'v3.20-next-arm64' of https://github.com/mbgg/linux-mediatek:
  arm64: mediatek: Add MT8173 SoC Kconfig and defconfig
  arm64: dts: Add mediatek MT8173 SoC and evaluation board dts and Makefile
  Document: DT: Add bindings for mediatek MT8173 SoC Platform
Signed-off-by: NOlof Johansson <olof@lixom.net>