drm/panel: lg-sw43408: use new streamlined MIPI DSI API

Use newer mipi_dsi_*_multi() functions in order to simplify and cleanup
panel's prepare() and unprepare() functions.

Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20240512-dsi-panels-upd-api-v2-7-e31ca14d102e@linaro.org


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240512-dsi-panels-upd-api-v2-7-e31ca14d102e@linaro.org