testfirmware: fix memory leak in testfirmware_init()
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 v5.15.86 by commit 357379d504c0c8b0834e206ad8c49e4b3c98ed4d, it was introduced in version v4.14 by commit c92316bf8e94830a0225f2e904cbdbd173768419. For more details please see the references link.