dt-bindings: timer: Add support for cadence TTC PWM

Cadence TTC can act as PWM device, it will be supported through
separate PWM framework based driver. Decision to configure
specific TTC device as PWM or clocksource/clockevent would
be done based on presence of "#pwm-cells" property.

Also, interrupt property is not required for TTC PWM driver.
Update bindings to support TTC PWM configuration.
Signed-off-by: Mubin Sayyed <mubin.sayyed@amd.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20240226093333.2581092-1-mubin.sayyed@amd.com

Documentation/devicetree/bindings/timer/cdns,ttc.yaml

@@ -32,12 +32,23 @@ properties:
     description: |
       Bit width of the timer, necessary if not 16.
 
+  "#pwm-cells":
+    const: 3
+
 required:
   - compatible
   - reg
-  - interrupts
   - clocks
 
+allOf:
+  - if:
+      not:
+        required:
+          - "#pwm-cells"
+    then:
+      required:
+        - interrupts
+
 additionalProperties: false
 
 examples:
@@ -50,3 +61,12 @@ examples:
         clocks = <&cpu_clk 3>;
         timer-width = <32>;
     };
+
+  - |
+    pwm: pwm@f8002000 {
+        compatible = "cdns,ttc";
+        reg = <0xf8002000 0x1000>;
+        clocks = <&cpu_clk 3>;
+        timer-width = <32>;
+        #pwm-cells = <3>;
+    };