dt-bindings: interrupt-controller: stm32-exti: document st,stm32mp13-exti

Support of STM32MP13 SoC implies to create a new compatible in order to
manage EXTI/GIC mapping changes.

Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220202140005.860-2-alexandre.torgue@foss.st.com

Author: Alexandre Torgue

Documentation/devicetree/bindings/interrupt-controller/st,stm32-exti.yaml

@@ -20,6 +20,7 @@ properties:
       - items:
           - enum:
               - st,stm32mp1-exti
+              - st,stm32mp13-exti
           - const: syscon
 
   "#interrupt-cells":