O3: Mark fetch stage as active if it faults.

Otherwise if the rest of the pipeline is idle then
fault will never propagate to commit to be handled,
causing CPU to deadlock.

src/cpu/o3/fetch_impl.hh

@@ -1264,6 +1264,8 @@ DefaultFetch<Impl>::fetch(bool &status_change)
         toDecode->insts[numInst] = instruction;
         toDecode->size++;
 
+        wroteToTimeBuffer = true;
+
         DPRINTF(Fetch, "[tid:%i]: Blocked, need to handle the trap.\n",tid);
 
         fetchStatus[tid] = TrapPending;