arm64: dts: renesas: r8a774b1: Add SYS-DMAC device nodes

Add sys-dmac[0-2] device nodes for RZ/G2N (R8A774B1) SoC.

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Link: https://lore.kernel.org/r/1569831527-1250-2-git-send-email-biju.das@bp.renesas.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>