dt-bindings: arm: stm32: Document IoT Box compatible

Document devicetree compatible of Shiratech IoT Box.
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>

Documentation/devicetree/bindings/arm/stm32/stm32.yaml

@@ -39,6 +39,7 @@ properties:
           - enum:
               - arrow,stm32mp157a-avenger96 # Avenger96
               - lxa,stm32mp157c-mc1
+              - shiratech,stm32mp157a-iot-box # IoT Box
               - shiratech,stm32mp157a-stinger96 # Stinger96
               - st,stm32mp157c-ed1
               - st,stm32mp157a-dk1