arm64: dts: renesas: r8a779g0: Add L3 cache controller

Describe the cache configuration for the first Cortex-A76 CPU core on
the Renesas R-Car V4H (R8A779G0) SoC.

Extracted from a larger patch in the BSP by Takeshi Kihara.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/dfd743b32198295afb78bc0ac337ef283fa3879a.1668429870.git.geert+renesas@glider.be