Service interruption via concurrent CXL region deletion

Race condition in the Linux kernel CXL region code allows local users with elevated privileges to interrupt service through concurrent deletion. The sysfs deletion path looked up and removed regions without holding regions_lock across the operation, allowing concurrent requests or root-device teardown to trigger duplicate deletion. Reachability requires privileged write access to CXL region sysfs controls and an existing CXL region; the bounded consequence is kernel availability loss, with no confidentiality impact reported.