dt-bindings: pinctrl: stm32: Add missing interrupts property

Driver use interrupt-parent field so update the bindings to allow it.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200513145935.22493-15-benjamin.gaignard@st.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/st,stm32-pinctrl.yaml

@@ -36,6 +36,9 @@ properties:
   pins-are-numbered: true
   hwlocks: true
 
+  interrupts:
+    maxItems: 1
+
   st,syscfg:
     allOf:
       - $ref: "/schemas/types.yaml#/definitions/phandle-array"