Faults generated at fetch are passed to the backend by creating a dummy nop instructi...

Faults generated at fetch are passed to the backend by creating a dummy nop instruction and giving it the fault.  This unifies front end faults and normal instruction faults.

cpu/checker/cpu.cc:
    Fixups for fetch fault being sent with the instruction.
cpu/o3/fetch_impl.hh:
cpu/ozone/front_end_impl.hh:
    Send any faults generated at fetch along with a fake nop instruction to the back end.  This avoids having to use direct communication to check if the entire front end has drained; it is naturally handled through the nop's fault being handled when it reaches the head of commit.
cpu/ozone/front_end.hh:
    Add extra status TrapPending.
cpu/ozone/lw_back_end_impl.hh:
    Fetch fault handled through a dummy nop carrying the fetch fault.

    Avoid putting Nops on the exeList.

--HG--
extra : convert_revision : 8d9899748b34c204763a49c48a9b5113864f5789