drm/panel: Fix a possible null-pointer dereference in jdi_panel_dsi_remove()

In jdi_panel_dsi_remove(), jdi is explicitly checked, indicating that it
may be NULL:

  if (!jdi)
    mipi_dsi_detach(dsi);

However, when jdi is NULL, the function does not return and continues by
calling jdi_panel_disable():

  err = jdi_panel_disable(&jdi->base);

Inside jdi_panel_disable(), jdi is dereferenced unconditionally, which can
lead to a NULL-pointer dereference:

  struct jdi_panel *jdi = to_panel_jdi(panel);
  backlight_disable(jdi->backlight);

To prevent such a potential NULL-pointer dereference, return early from
jdi_panel_dsi_remove() when jdi is NULL.

Signed-off-by: Tuo Li <islituo@gmail.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patch.msgid.link/20251218120955.11185-1-islituo@gmail.com

Author: lituo1996

drivers/gpu/drm/panel/panel-jdi-lpm102a188a.c

@@ -434,8 +434,10 @@ static void jdi_panel_dsi_remove(struct mipi_dsi_device *dsi)
 	int err;
 
 	/* only detach from host for the DSI-LINK2 interface */
-	if (!jdi)
+	if (!jdi) {
 		mipi_dsi_detach(dsi);
+		return;
+	}
 
 	err = jdi_panel_disable(&jdi->base);
 	if (err < 0)