drm/panel: xinpeng-xpp055c272: Don't call unprepare+disable at shutdown/remove

It's the responsibility of a correctly written DRM modeset driver to
call drm_atomic_helper_shutdown() at shutdown time and that should be
disabling / unpreparing the panel if needed. Panel drivers shouldn't
be calling these functions themselves.

A recent effort was made to fix as many DRM modeset drivers as
possible [1] [2] [3] and most drivers are fixed now.

A grep through mainline for compatible strings used by this driver
indicates that it is used by Rockchip boards. The Rockchip driver
appears to be correctly calling drm_atomic_helper_shutdown() so we can
remove the calls.

[1] https://lore.kernel.org/r/20230901234015.566018-1-dianders@chromium.org
[2] https://lore.kernel.org/r/20230901234202.566951-1-dianders@chromium.org
[3] https://lore.kernel.org/r/20230921192749.1542462-1-dianders@chromium.orgAcked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240503143327.RFT.v2.31.Ib97e67a9877070698afbec4f8ede091b2bf89a1f@changeid

drivers/gpu/drm/panel/panel-xinpeng-xpp055c272.c

@@ -306,27 +306,11 @@ static int xpp055c272_probe(struct mipi_dsi_device *dsi)
 	return 0;
 }
 
-static void xpp055c272_shutdown(struct mipi_dsi_device *dsi)
-{
-	struct xpp055c272 *ctx = mipi_dsi_get_drvdata(dsi);
-	int ret;
-
-	ret = drm_panel_unprepare(&ctx->panel);
-	if (ret < 0)
-		dev_err(&dsi->dev, "Failed to unprepare panel: %d\n", ret);
-
-	ret = drm_panel_disable(&ctx->panel);
-	if (ret < 0)
-		dev_err(&dsi->dev, "Failed to disable panel: %d\n", ret);
-}
-
 static void xpp055c272_remove(struct mipi_dsi_device *dsi)
 {
 	struct xpp055c272 *ctx = mipi_dsi_get_drvdata(dsi);
 	int ret;
 
-	xpp055c272_shutdown(dsi);
-
 	ret = mipi_dsi_detach(dsi);
 	if (ret < 0)
 		dev_err(&dsi->dev, "Failed to detach from DSI host: %d\n", ret);
@@ -347,7 +331,6 @@ static struct mipi_dsi_driver xpp055c272_driver = {
 	},
 	.probe	= xpp055c272_probe,
 	.remove = xpp055c272_remove,
-	.shutdown = xpp055c272_shutdown,
 };
 module_mipi_dsi_driver(xpp055c272_driver);