drm/mediatek: Add missing put_device() call in mtk_ddp_comp_init()

if of_find_device_by_node() succeed, mtk_ddp_comp_init() doesn't have
a corresponding put_device(). Thus add put_device() to fix the exception
handling for this function implementation.

Fixes: d0afe37f ("drm/mediatek: support CMDQ interface in ddp component")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>