Changeset 10683:3147f3a868f7
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mem: fix prefetcher bug regarding write buffer hits

Prefetches are supposed to be squashed if the block is already
present in a higher-level cache.  We squash appropriately if
the block is in a higher-level cache or MSHR, but did not
properly handle the case where the block is in the write buffer.

Thanks to George Michelogiannakis <mihelog@lbl.gov> for
help in tracking down and testing this fix.