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 v5.15.19 by commit e33fa4a46ee22de88a700e2e3d033da8214a5175, it was introduced in version v5.6 by commit d380dcde9a07ca5de4805dee11f58a98ec0ad6ff. For more details please see the references link.