Second M_WAITOK-sleep-reachable-inside-critical-section site: fw_bus_probe() holds crit_enter() across fw_bus_explore()'s device kmalloc(M_WAITOK|M_ZERO) (distinct from known DF-1021/fw_get_tlabel)

Summary

fw_bus_probe wraps the whole exploration in crit_enter and fw_bus_explore kmallocs a new fw_device with M_WAITOK when a fresh EUI64 answers - same class as DF-1021 but a call site its fix would not cover; scheduler/livelock hazard under memory pressure on real hardware. Hardware+pressure-gated. M_INTWAIT-or-move-out-of-crit fix.