Apply clang-tidy fixes for llvm-qualified-auto in LowerToLLVM.cpp (NFC)

mlir/examples/toy/Ch6/mlir/LowerToLLVM.cpp

@@ -61,7 +61,7 @@ public:
   LogicalResult
   matchAndRewrite(Operation *op, ArrayRef<Value> operands,
                   ConversionPatternRewriter &rewriter) const override {
-    auto context = rewriter.getContext();
+    auto *context = rewriter.getContext();
     auto memRefType = llvm::cast<MemRefType>((*op->operand_type_begin()));
     auto memRefShape = memRefType.getShape();
     auto loc = op->getLoc();