drm/panthor: Fix UAF in panthor_gem_create_with_handle() debugfs code

In the Linux kernel, the following vulnerability has been resolved: drm/panthor: Fix UAF in panthor_gem_create_with_handle() debugfs code The object is potentially already gone after the drm_gem_object_put(). In general the object should be fully constructed before calling drm_gem_handle_create(), except the debugfs tracking uses a separate lock and list and separate flag to denotate whether the object is actually initialized. Since I'm touching this all anyway simplify this by only adding the object to the debugfs when it's ready for that, which allows us to delete that separate flag. panthor_gem_debugfs_bo_rm() already checks whether we've actually been added to the list or this is some error path cleanup. v2: Fix build issues for !CONFIG_DEBUGFS (Adrián) v3: Add linebreak and remove outdated comment (Liviu)

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Linux kernel 安全漏洞

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于drm/panthor模块在panthor_gem_create_with_handle函数中可能导致释放后重用。

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