[PowerPC] Re-enable VSX test line for fma.ll with -mcpu=pwr7
The VSX testing variant in test/CodeGen/PowerPC/fma.ll had to be
disabled because of unexpected behavior on many of the builders. I
tracked this down to a situation that occurs when the VSX attribute is
enabled for a target that disables the MI early scheduling pass. This
patch adds -mcpu=pwr7 to make this predictable. The other issue will
be addressed separately.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220171
91177308-0d34-0410-b5e6-
96231b3b80d8