dt-bindings: net: silabs,wfx: add prt,prtt1c-wfm200 antenna variant

Add compatible for wfm200 antenna configuration variant for Protonic PRTT1C
board.
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

Documentation/devicetree/bindings/staging/net/wireless/silabs,wfx.yaml

@@ -39,6 +39,7 @@ properties:
   compatible:
     items:
       - enum:
+          - prt,prtt1c-wfm200 # Protonic PRTT1C Board
           - silabs,brd4001a # WGM160P Evaluation Board
           - silabs,brd8022a # WF200 Evaluation Board
           - silabs,brd8023a # WFM200 Evaluation Board