dt-bindings: pwm: renesas,tpu-pwm: Improve json-schema

  - Include the general PWM controller schema,
  - Make clocks, power-domains, and resets properties required.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: https://lore.kernel.org/r/d36e3690ce8c5a1e53d054552e4fd8b90d6a5478.1620648868.git.geert+renesas@glider.be


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