dt-bindings: pwm: intel,lgm: 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>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

Author: krzk

Documentation/devicetree/bindings/pwm/intel,lgm-pwm.yaml

@@ -9,6 +9,9 @@ title: LGM SoC PWM fan controller
 maintainers:
   - Rahul Tanwar <rtanwar@maxlinear.com>
 
+allOf:
+  - $ref: pwm.yaml#
+
 properties:
   compatible:
     const: intel,lgm-pwm