Disable opaque pointers when converting SPIR-V to LLVM

Temporarily disable opaque pointers when running `llvm-spirv -r`,
after LLVM upstream commit 41d5033 ("[IR] Enable opaque pointers
by default", 2022-06-02).

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@1e0b516

Author: svenvh

llvm-spirv/tools/llvm-spirv/llvm-spirv.cpp

@@ -344,6 +344,8 @@ static bool isFileEmpty(const std::string &FileName) {
 
 static int convertSPIRVToLLVM(const SPIRV::TranslatorOpts &Opts) {
   LLVMContext Context;
+  Context.setOpaquePointers(false);
+
   std::ifstream IFS(InputFile, std::ios::binary);
   Module *M;
   std::string Err;