drm/panel: raydium-rm67191: Don't call unprepare+disable at shutdown

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 IMX boards. The IMX 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.org

Cc: Robert Chiras <robert.chiras@nxp.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20240604172305.v3.22.Id14188f1a8af7d524751c27c343a5b583ff5361f@changeidSigned-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240604172305.v3.22.Id14188f1a8af7d524751c27c343a5b583ff5361f@changeid

drivers/gpu/drm/panel/panel-raydium-rm67191.c

@@ -612,14 +612,6 @@ static void rad_panel_remove(struct mipi_dsi_device *dsi)
 	drm_panel_remove(&rad->panel);
 }
 
-static void rad_panel_shutdown(struct mipi_dsi_device *dsi)
-{
-	struct rad_panel *rad = mipi_dsi_get_drvdata(dsi);
-
-	drm_panel_disable(&rad->panel);
-	drm_panel_unprepare(&rad->panel);
-}
-
 static const struct of_device_id rad_of_match[] = {
 	{ .compatible = "raydium,rm67191", },
 	{ /* sentinel */ }
@@ -633,7 +625,6 @@ static struct mipi_dsi_driver rad_panel_driver = {
 	},
 	.probe = rad_panel_probe,
 	.remove = rad_panel_remove,
-	.shutdown = rad_panel_shutdown,
 };
 module_mipi_dsi_driver(rad_panel_driver);