drm/mediatek: mtk_dpi: Switch to devm_drm_of_get_bridge()

Function drm_of_find_panel_or_bridge() is marked as deprecated: since
the usage of that in this driver exactly corresponds to the new function
devm_drm_of_get_bridge(), switch to it.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Fei Shao <fshao@chromium.org>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20230726082245.550929-4-angelogioacchino.delregno@collabora.com/


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