CVE-2025-38215 fbdev: Fix do_register_framebuffer to prevent null-ptr-deref in fb_videomode_to_var

In the Linux kernel, the following vulnerability has been resolved: fbdev: Fix doregisterframebuffer to prevent null-ptr-deref in fbvideomodetovar If fbaddvideomode in doregisterframebuffer fails to allocate memory for fbvideomode, it will later lead to a null-ptr dereference in fbvideomodetovar,...