drm/panel: visionox-rm69299: stop calling regulator_set_load manually

Use .init_load_uA part of the bulk regulator API instead of calling
register_set_load() manually.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20240404-drop-panel-unregister-v1-6-9f56953c5fb9@linaro.org
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240404-drop-panel-unregister-v1-6-9f56953c5fb9@linaro.org