[llvm-mca] Constify SourceMgr::hasNext.  NFC.

llvm-svn: 336961
diff --git a/llvm/tools/llvm-mca/SourceMgr.h b/llvm/tools/llvm-mca/SourceMgr.h
index afde35f..15a85a6 100644
--- a/llvm/tools/llvm-mca/SourceMgr.h
+++ b/llvm/tools/llvm-mca/SourceMgr.h
@@ -40,7 +40,7 @@
   unsigned size() const { return Sequence.size(); }
   const InstVec &getSequence() const { return Sequence; }
 
-  bool hasNext() { return Current < (Iterations * size()); }
+  bool hasNext() const { return Current < (Iterations * size()); }
   void updateNext() { Current++; }
 
   const SourceRef peekNext() const {