drm/panel: ilitek-ili9881c: make use of prepare_prev_first

The panel.prepare() call requires an initialized MIPI-DSI host, so set
the prepare_prev_first flag to indicate that the host must be
initialized first.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20231123-drm-panel-ili9881c-am8001280g-v1-1-fdf4d624c211@pengutronix.de


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231123-drm-panel-ili9881c-am8001280g-v1-1-fdf4d624c211@pengutronix.de