Add everything needed to support the DSI output on Renesas r8a779h0
(V4M) SoC, and the DP output (via sn65dsi86 DSI to DP bridge) on the
Renesas grey-hawk board.
Overall the DSI and the board design is almost identical to Renesas
r8a779g0 and white-hawk board.
Note: the v4 no longer has the dts and the clk patches, as those have
been merged to renesas-devel.