arm64: dts: renesas: Add Renesas R8A779MB SoC support

Add support for the Renesas R-Car H3Ne-1.7G (R8A779MB) 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/862a5eecc850cbb90af86a56513b644b638fb62b.1656072871.git.geert+renesas@glider.be