drm: bridge: dw_hdmi: Switch to of_graph_get_remote_node()

To reduce boilerplate, use of_graph_get_remote_node() helper instead of
the hand-rolling code.

Signed-off-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20240316170513.1159724-1-sui.jingfeng@linux.dev


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240316170513.1159724-1-sui.jingfeng@linux.dev