arm64: dts: renesas: r8a774a1: Add CMT device nodes

This patch adds the CMT[0123] device tree nodes to the
r8a774a1 SoC specific DT.

Signed-off-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>