drm/mediatek: Fix device node reference leak in mtk_dp_dt_parse()

drm/mediatek: Fix device node reference leak in mtk_dp_dt_parse()

The function mtk_dp_dt_parse() calls of_graph_get_endpoint_by_regs()
to get the endpoint device node, but fails to call of_node_put() to release
the reference when the function returns. This results in a device node
reference leak.

Fix this by adding the missing of_node_put() call before returning from
the function.

Found via static analysis and code review.

Fixes: f70ac097a2cf ("drm/mediatek: Add MT8195 Embedded DisplayPort driver")
Cc: stable@vger.kernel.org
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Reviewed-by: Markus Schneider-Pargmann <msp@baylibre.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20251029072307.10955-1-linmq006@gmail.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>