[llvm-exegesis] move Mode from Key to BenchmarResult.

Moves the Mode field out of the Key. The existing yaml benchmark results can be fixed with the following script:

```
readonly FILE=$1
readonly MODE=latency # Change to uops to fix a uops benchmark.
cat $FILE | \
  sed "/^\ \+mode:\ \+$MODE$/d" | \
  sed "/^cpu_name.*$/i mode:            $MODE"
```

Differential Revision: https://reviews.llvm.org/D47813

Authored by: Guillaume Chatelet

llvm-svn: 334079
diff --git a/llvm/tools/llvm-exegesis/lib/Latency.cpp b/llvm/tools/llvm-exegesis/lib/Latency.cpp
index 633189e..9c4ed56 100644
--- a/llvm/tools/llvm-exegesis/lib/Latency.cpp
+++ b/llvm/tools/llvm-exegesis/lib/Latency.cpp
@@ -52,8 +52,8 @@
 
 LatencyBenchmarkRunner::~LatencyBenchmarkRunner() = default;
 
-InstructionBenchmarkKey::ModeE LatencyBenchmarkRunner::getMode() const {
-  return InstructionBenchmarkKey::Latency;
+InstructionBenchmark::ModeE LatencyBenchmarkRunner::getMode() const {
+  return InstructionBenchmark::Latency;
 }
 
 llvm::Expected<std::vector<llvm::MCInst>>