drm/panel: synaptics-r63353: Fix regulator unbalance

The shutdown function can be called when the display is already
unprepared. For example during reboot this trigger a kernel
backlog. Calling the drm_panel_unprepare, allow us to avoid
to trigger the kernel warning.

Fixes: 2e87bad ("drm/panel: Add Synaptics R63353 panel driver")
Tested-by: Dario Binacchi <[email protected]>
Signed-off-by: Michael Trimarchi <[email protected]>
Signed-off-by: Dario Binacchi <[email protected]>
Reviewed-by: Neil Armstrong <[email protected]>
Reviewed-by: Jessica Zhang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Neil Armstrong <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: panicking

drivers/gpu/drm/panel/panel-synaptics-r63353.c

@@ -325,7 +325,7 @@ static void r63353_panel_shutdown(struct mipi_dsi_device *dsi)
 {
 	struct r63353_panel *rpanel = mipi_dsi_get_drvdata(dsi);
 
-	r63353_panel_unprepare(&rpanel->base);
+	drm_panel_unprepare(&rpanel->base);
 }
 
 static const struct r63353_desc sharp_ls068b3sx02_data = {