cxl/region: Fix cxl_region leak, cleanup targets at region delete

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: cxl/region: Fix cxl_region leak, cleanup targets at region delete When a region is deleted any targets that have been previously assigned to that region hold references to it. Trigger those references to drop by detaching all targets at unregister_region() time. Otherwise that region object will leak as userspace has lost the ability to detach targets once region sysfs is torn down.

References

• https://git.kernel.org/stable/c/45d9fb4b758b9d602ee7776eb6754b0349946aad
• https://git.kernel.org/stable/c/0d9e734018d70cecf79e2e4c6082167160a0f13f