CVE-2026-72170 9p: skip nlink update in cacheless mode to fix WARN_ON

In the Linux kernel, the following vulnerability has been resolved: 9p: skip nlink update in cacheless mode to fix WARNON v9fsdeccount unconditionally calls dropnlink on regular files, even when the inode's nlink is already zero. In cacheless mode the client refetches inode metadata from the serv...