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

commit 1c4b5ecb ("remove the h8300 architecture") removes Renesas TPU
timer driver. Let's remove its binding documentation.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/87semglt2g.wl-kuninori.morimoto.gx@renesas.com


Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>