arm64: dts: renesas: Add Renesas R8A779M7 SoC support

Add support for the Renesas R-Car D3e (R8A779M7) SoC, which is a
different grading of the R-Car D3 (R8A77995) SoC.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/2aa5b34d5b50f757092bc6442bb59a8534f2ff24.1628766192.git.geert+renesas@glider.be