drm/mediatek: ovl_adaptor: Add missing of_node_put()

Error paths that exit for_each_child_of_node() need to call
of_node_put() to decerement the child refcount and avoid memory leaks.

Add the missing of_node_put().

Cc: stable@vger.kernel.org
Fixes: 453c3364 ("drm/mediatek: Add ovl_adaptor support for MT8195")
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20240624-mtk_disp_ovl_adaptor_scoped-v1-2-9fa1e074d881@gmail.com/


Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>