arm64: dts: renesas: Add Renesas R8A779M4 SoC support

Add support for the Renesas R-Car M3Ne (R8A779M4) SoC, which is a
different grading of the R-Car M3-N (R8A77965) SoC.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/52aa6dcf6682f54fa2bf53491ef7de5173192a73.1628766192.git.geert+renesas@glider.be