dt-bindings: serial: mediatek,uart: add MT6572

Add a compatible string for serial on the MT6572 SoC.

Acked-by: Krzysztof Kozlowski <[e-mail]>
Reviewed-by: AngeloGioacchino Del Regno <[e-mail]>
Signed-off-by: Max Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/serial/mediatek,uart.yaml

···
           - enum:
               - mediatek,mt2701-uart
               - mediatek,mt2712-uart
+              - mediatek,mt6572-uart
               - mediatek,mt6580-uart
               - mediatek,mt6582-uart
               - mediatek,mt6589-uart