linux-phytec-fsl

arm: add basic support for Mediatek MT6589 boards

This adds a generic devicetree board file and a dtsi for boards
based on MT6589 SoCs from Mediatek.

Apart from the generic parts (gic, clocks) the only component
currently supported are the timers.

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