dt-bindings: timer: renesas,tpu: remove obsolete binding

Commit 1c4b5ecb ("remove the h8300 architecture") removed Renesas
TPU timer driver. Let's remove its binding.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/877c3vnq0k.wl-kuninori.morimoto.gx@renesas.com


Signed-off-by: Rob Herring (Arm) <robh@kernel.org>