arm64: dts: renesas: r8a77965: Add dmac device nods

Add dmac[0-2] device nodes for R-Car M3-N (r8a77965) SoC.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>