dt-bindings: timer: renesas,tmu: Add R-Car V4M support

Document support for the Timer Unit (TMU) in the Renesas R-Car V4M
(R8A779H0) SoC.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/8a39386b1a33db6e83e852b3b365bc1adeb25242.1712068574.git.geert+renesas@glider.be


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