CVE-2026-46100 fs: afs: revert mmap_prepare() change

In the Linux kernel, the following vulnerability has been resolved: fs: afs: revert mmapprepare change Partially reverts commit 9d5403b1036c "fs: convert most other genericfilemmap users to .mmapprepare". This is because the .mmap invocation establishes a refcount, but .mmapprepare is called at a...