arm64: dts: renesas: Add Renesas R8A779M8 SoC support

Add support for the Renesas R-Car H3Ne (R8A779M8) SoC, which is a
different grading of the R-Car H3-N (R8A77951) SoC.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/99ff5658889e22ea8e723733e6972c27370930bf.1628766192.git.geert+renesas@glider.be