arm64: dts: renesas: r8a779a0: Update to R-Car Gen4 compatible values

Despite the name, R-Car V3U is the first member of the R-Car Gen4
family.  Hence update the compatible properties in various device nodes
to include family-specific compatible values for R-Car Gen4 instead of
R-Car Gen3:
  - EtherAVB,
  - MSIOF.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/387168aef20d399d4f4318f4ecab9c3b016fd6f2.1666605756.git.geert+renesas@glider.be