Fix the O3CPU to support the multi-pass method for checking if the system has fully...

Fix the O3CPU to support the multi-pass method for checking if the system has fully drained.

src/cpu/o3/commit.hh:
src/cpu/o3/commit_impl.hh:
src/cpu/o3/decode.hh:
src/cpu/o3/decode_impl.hh:
src/cpu/o3/fetch.hh:
src/cpu/o3/fetch_impl.hh:
src/cpu/o3/iew.hh:
src/cpu/o3/iew_impl.hh:
src/cpu/o3/rename.hh:
src/cpu/o3/rename_impl.hh:
    Return a value so that the CPU can instantly return from draining if the pipeline is already drained.
src/cpu/o3/cpu.cc:
    Use values returned from pipeline stages so that the CPU can instantly return from draining if the pipeline is already drained.

--HG--
extra : convert_revision : d8ef6b811644ea67c8b40c4719273fa224105811