ring-buffer: Fix buffer locking in ring_buffer_subbuf_order_set()

In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Fix buffer locking in ring_buffer_subbuf_order_set() Enlarge the critical section in ring_buffer_subbuf_order_set() to ensure that error handling takes place with per-buffer mutex held, thus preventing list corruption and other concurrency-related issues.