arm64: dts: renesas: Add Renesas R8A779M5 SoC support

Add support for the Renesas R-Car M3Ne-2G (R8A779M5) 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/2ed19a0e009d3e7afb330086b69c8724465b88cc.1628766192.git.geert+renesas@glider.be