arm64: dts: renesas: rcar-gen3: Add missing TMU nodes

Add device nodes for the Timer Unit (TMU) on the Renesas R-Car H3
(r8a77951), M3-W (r8a77960), M3-W+ (r8a77961), M3-N (r8a77965), E3
(r8a77990), and D3 (r8a77995) SoCs.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/20201210152705.1535156-2-niklas.soderlund+renesas@ragnatech.se


[geert: squashed six commits]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>