CVE-2026-46187: wifi: rsi: fix kthread lifetime race between self-exit and external-stop

In the Linux kernel, the following vulnerability has been resolved:

wifi: rsi: fix kthread lifetime race between self-exit and external-stop

RSI driver use both self-exit(kthreadcompleteandexit) and external-stop (kthreadstop) when killing a kthread. Generally, kthreadstop() is called first, and in this case, no particular issues occur.

However, in rare instances where kthreadcompleteandexit() is called first and then kthreadstop() is called, a UAF occurs because the kthread object, which has already exited and been freed, is accessed again.

Therefore, to prevent this with minimal modification, you must remove kthreadstop() and change the code to wait until the self-exit operation is completed.