Add V3M Starter Kit board support

Hello.

Here's the set of 2 patches against Simon Horman's 'renesas.git' repo's 'renesas-devel-20171124v2-v4.14' tag. I'm adding the device tree support for the R8A77970-based V3M Starter Kit board.

[1/2] arm64: dts: renesas: initial V3MSK board device tree [2/2] arm64: dts: renesas: v3msk: add EtherAVB support

WBR, Sergei