drm/gma500: fix null pointer dereference in cdv_intel_lvds_get_modes

In the Linux kernel, the following vulnerability has been resolved: drm/gma500: fix null pointer dereference in cdv_intel_lvds_get_modes In cdv_intel_lvds_get_modes(), the return value of drm_mode_duplicate() is assigned to mode, which will lead to a NULL pointer dereference on failure of drm_mode_duplicate(). Add a check to avoid npd.