[llvm-cov] Rename ShowFormat to Format (NFC)

This makes it a bit more generic, in case we want to emit summary
reports in different formats in the future.

llvm-svn: 274026
diff --git a/llvm/tools/llvm-cov/SourceCoverageView.cpp b/llvm/tools/llvm-cov/SourceCoverageView.cpp
index b71a35f..d6de961 100644
--- a/llvm/tools/llvm-cov/SourceCoverageView.cpp
+++ b/llvm/tools/llvm-cov/SourceCoverageView.cpp
@@ -97,7 +97,7 @@
 SourceCoverageView::create(StringRef SourceName, const MemoryBuffer &File,
                            const CoverageViewOptions &Options,
                            coverage::CoverageData &&CoverageInfo) {
-  switch (Options.ShowFormat) {
+  switch (Options.Format) {
   case CoverageViewOptions::OutputFormat::Text:
     return llvm::make_unique<SourceCoverageViewText>(SourceName, File, Options,
                                                      std::move(CoverageInfo));