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.xyz


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>