tracing/histogram: Fix a potential memory leak for kstrdup()
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v5.10.96 by commit d71b06aa995007eafd247626d0669b9364c42ad7, it was introduced in version v5.6 by commit d380dcde9a07ca5de4805dee11f58a98ec0ad6ff. For more details please see the references link.