Have bus use the BadAddress device to handle bad addresses. The O3 CPU should be...

Have bus use the BadAddress device to handle bad addresses.  The O3 CPU should be able to boot into Linux with caches on after this change.

src/mem/bus.cc:
src/mem/bus.hh:
    Bus now will be setup with a default responder, unless the user overrides it.  This default responder should return BadAddress if no matching port is found.
src/python/m5/objects/Bus.py:
    Bus now has a default responder for FS mode if the user doesn't override it.  It returns BadAddress if no matching port is found.
src/python/m5/objects/Tsunami.py:
    Add bad address device.  Also record when the user has specified their own default responder.

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extra : convert_revision : 59070477ae313ee711b2d59baa2369c9a91c5b85