drm/mediatek: Fix device use-after-free on unbind

In the Linux kernel, the following vulnerability has been resolved: drm/mediatek: Fix device use-after-free on unbind A recent change fixed device reference leaks when looking up drm platform device driver data during bind() but failed to remove a partial fix which had been added by commit 80805b62ea5b ("drm/mediatek: Fix kobject put for component sub-drivers"). This results in a reference imbalance on component bind() failures and on unbind() which could lead to a user-after-free. Make sure to only drop the references after retrieving the driver data by effectively reverting the previous partial fix. Note that holding a reference to a device does not prevent its driver data from going away so there is no point in keeping the reference.