[Driver][Mips] Restore FIXME comment was removed accidentally.

llvm-svn: 213734
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index f62cb85..0a123a6 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -952,6 +952,8 @@
       .Cases("n32", "n64", DefMips64CPU)
       .Default("");
   }
+
+  // FIXME: Warn on inconsistent use of -march and -mabi.
 }
 
 // Convert ABI name to the GNU tools acceptable variant.