pwm: atmel: Add PWM binding for SAM9X60

Add PWM binding for SAM9X60 SoC.
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

Documentation/devicetree/bindings/pwm/atmel-pwm.txt

@@ -5,6 +5,7 @@ Required properties:
     - "atmel,at91sam9rl-pwm"
     - "atmel,sama5d3-pwm"
     - "atmel,sama5d2-pwm"
+    - "microchip,sam9x60-pwm"
   - reg: physical base address and length of the controller's registers
   - #pwm-cells: Should be 3. See pwm.txt in this directory for a
     description of the cells format.