dt-bindings: arm: stm32: Document Ultratronik's Fly board DT binding

This commit documents ultra-fly-sbc devicetree binding based on
STM32MP157 SoC.

Signed-off-by: Goran Rađenović <[email protected]>
Acked-by: Rob Herring (Arm) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexandre Torgue <[email protected]>

Author: Goran Rađenović

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

@@ -188,6 +188,11 @@ properties:
           - const: phytec,phycore-stm32mp157c-som
           - const: st,stm32mp157
 
+      - description: Ultratronik STM32MP1 SBC based Boards
+        items:
+          - const: ultratronik,stm32mp157c-ultra-fly-sbc
+          - const: st,stm32mp157
+
       - description: ST STM32MP257 based Boards
         items:
           - enum: