Correct fdot test RUN line

Author: pow2clk

llvm/test/CodeGen/DirectX/fdot.ll

@@ -1,5 +1,5 @@
 ; RUN: opt -S  -dxil-intrinsic-expansion -mtriple=dxil-pc-shadermodel6.3-library %s | FileCheck %s --check-prefixes=CHECK,EXPCHECK
-; RUN: opt -S  -dxil-op-lower -mtriple=dxil-pc-shadermodel6.3-library %s | FileCheck %s
+; RUN: opt -S  -dxil-op-lower -mtriple=dxil-pc-shadermodel6.3-library %s | FileCheck %s --check-prefixes=CHECK,DOPCHECK
 
 ; Make sure dxil operation function calls for dot are generated for float type vectors.