Enabling 3DNow! prefetch instruction for a few AMD processors: bobcat, jaguar,
bulldozer and piledriver. Support for the instruction itself seems to have
already been added in r178040.

Differential Revision: http://llvm-reviews.chandlerc.com/D1933



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192828 91177308-0d34-0410-b5e6-96231b3b80d8