arm64: dts: renesas: r8a779g0: Add DMA support

Add device nodes for the Direct Memory Access Controllers for System
(SYS-DMAC) on the Renesas R-Car V4H (R8A779G0) SoC.

Link all DMA consumers to the corresponding DMA controller channels.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/1ea45b51f897a11d9477be4ac54fdb0efcc624e1.1664204771.git.geert+renesas@glider.be