dt-bindings: timer: renesas: tmu: Document r8a774e1 bindings

Document RZ/G2H (R8A774E1) SoC in the Renesas TMU bindings.
Signed-off-by: Marian-Cristian Rotariu <marian-cristian.rotariu.rb@bp.renesas.com>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20201110162014.3290109-2-geert+renesas@glider.be

Documentation/devicetree/bindings/timer/renesas,tmu.txt

@@ -13,6 +13,7 @@ Required Properties:
     - "renesas,tmu-r8a774a1" for the r8a774A1 TMU
     - "renesas,tmu-r8a774b1" for the r8a774B1 TMU
     - "renesas,tmu-r8a774c0" for the r8a774C0 TMU
+    - "renesas,tmu-r8a774e1" for the r8a774E1 TMU
     - "renesas,tmu-r8a7778" for the r8a7778 TMU
     - "renesas,tmu-r8a7779" for the r8a7779 TMU
     - "renesas,tmu-r8a77970" for the r8a77970 TMU