dt-bindings: arm: Add MT6589 Fairphone 1

Add the compatible for Fairphone 1 smartphone with MT6589 SoC.
Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Link: https://lore.kernel.org/r/20211005202833.96526-1-luca@z3ntu.xyzSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>

Documentation/devicetree/bindings/arm/mediatek.yaml

@@ -32,6 +32,7 @@ properties:
           - const: mediatek,mt6580
       - items:
           - enum:
+              - fairphone,fp1
               - mundoreader,bq-aquaris5
           - const: mediatek,mt6589
       - items: