ARM: dts: r8a77470: Add SCIF support

Describe SCIF ports in the R8A77470 device tree.
Also it fixes the CPG clock index ZS from 6 to 5.

Fixes: 6929dfc5 ("ARM: dts: r8a77470: Initial SoC device tree")
Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>