arm64: dts: renesas: r8a77961: Add SCIF and HSCIF nodes

Add the device nodes for all SCIF and HSCIF serial ports on R-Car M3-W+.
Add the missing DMA properties to the already-present SCIF2 node.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Eugeniu Rosca <erosca@de.adit-jv.com>