[llvm-exegesis] Use BenchmarkResult::Instructions instead of OpcodeName

Summary:
Get rid of OpcodeName.

To remove the opcode name from an old file:
```
cat old_file | sed '/opcode_name.*/d'
```

Reviewers: gchatelet

Subscribers: tschuett, llvm-commits

Differential Revision: https://reviews.llvm.org/D48121

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@334691 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed