CVE-2023-53864 drm/mxsfb: Disable overlay plane in mxsfb_plane_overlay_atomic_disable()

In the Linux kernel, the following vulnerability has been resolved: drm/mxsfb: Disable overlay plane in mxsfbplaneoverlayatomicdisable When disabling overlay plane in mxsfbplaneoverlayatomicupdate, overlay plane's framebuffer pointer is NULL. So, dereferencing it would cause a kernel OopsNULL...