drm/mediatek: unbind components in mtk_drm_unbind()

Unbinding components (i.e. mtk_dsi and mtk_disp_ovl/rdma/color) will
trigger master(mtk_drm)'s .unbind(), and currently mtk_drm's unbind
won't actually unbind components. During the next bind,
mtk_drm_kms_init() is called, and the components are added back.

.unbind() should call mtk_drm_kms_deinit() to unbind components.

And since component_master_del() in .remove() will trigger .unbind(),
which will also unregister device, it's fine to remove original functions
called here.

Fixes: 119f5173 ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.")
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Signed-off-by: CK Hu <ck.hu@mediatek.com>