CVE-2026-46095: md/md-llbitmap: raise barrier before state machine transition

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

md/md-llbitmap: raise barrier before state machine transition

Move the barrier raise operation before calling llbitmapstatemachine() in both llbitmapstartwrite() and llbitmapstartdiscard(). This ensures the barrier is in place before any state transitions occur, preventing potential race conditions where the state machine could complete before the barrier is properly raised.