[Kaleidoscope] toy.cpp use after move fix

The variable Proto is moved at the beginning of the codegen() function.
According to the comment above, the pointed object should be used due the
reference P.

Differential Revision: https://reviews.llvm.org/D32939

llvm-svn: 302369
diff --git a/llvm/examples/Kaleidoscope/Chapter7/toy.cpp b/llvm/examples/Kaleidoscope/Chapter7/toy.cpp
index 2f8cb68..79ac7b3 100644
--- a/llvm/examples/Kaleidoscope/Chapter7/toy.cpp
+++ b/llvm/examples/Kaleidoscope/Chapter7/toy.cpp
@@ -1099,7 +1099,7 @@
   TheFunction->eraseFromParent();
 
   if (P.isBinaryOp())
-    BinopPrecedence.erase(Proto->getOperatorName());
+    BinopPrecedence.erase(P.getOperatorName());
   return nullptr;
 }