Replace a few more "fall through" comments with LLVM_FALLTHROUGH

Follow up to r278902. I had missed "fall through", with a space.

llvm-svn: 278970
diff --git a/llvm/lib/Analysis/TargetLibraryInfo.cpp b/llvm/lib/Analysis/TargetLibraryInfo.cpp
index 8569c4d..2a47390 100644
--- a/llvm/lib/Analysis/TargetLibraryInfo.cpp
+++ b/llvm/lib/Analysis/TargetLibraryInfo.cpp
@@ -324,6 +324,7 @@
     // on Linux.
     //
     // Fall through to disable all of them.
+    LLVM_FALLTHROUGH;
   default:
     TLI.setUnavailable(LibFunc::exp10);
     TLI.setUnavailable(LibFunc::exp10f);