drm/mediatek: Delete not used of_device_get_match_data

The driver will be loaded by via a platform device. So we
will need to get the device_node from the parent device.
Depending on this we will set the driver data.
As all this is done later already, just delete the call to
of_device_get_match_data.

Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>