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:
  - DMAC,
  - (H)SCIF,
  - I2C,
  - IPMMU,
  - WDT.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/73cea9d5e1a6639422c67e4df4285042e31c9fd5.1651497071.git.geert+renesas@glider.be