dt-bindings: pwm: renesas,pwm: Include generic PWM schema

Include generic pwm.yaml schema, which enforces PWM node naming and
brings pwm-cells requirement.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

Documentation/devicetree/bindings/pwm/renesas,pwm-rcar.yaml

@@ -59,11 +59,13 @@ properties:
 required:
   - compatible
   - reg
-  - '#pwm-cells'
   - clocks
   - power-domains
 
-if:
+allOf:
+  - $ref: pwm.yaml#
+
+  - if:
       not:
         properties:
           compatible:
@@ -71,7 +73,7 @@ if:
               enum:
                 - renesas,pwm-r8a7778
                 - renesas,pwm-r8a7779
-then:
+    then:
       required:
         - resets