dt-bindings: timer: renesas,tmu: Add R-Mobile APE6 support

dt-bindings: timer: renesas,tmu: Add R-Mobile APE6 support

Document support for the Timer Unit (TMU) on the R-Mobile APE6 (R8A73A4)
Soc.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/17e3fd5f27ab540c8611545ad3dc5a697ca66c58.1716985096.git.geert+renesas@glider.be
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>