[NFC][SYCL][clang] Fix -Wunused-private-field warnings in SemaSYCL (#9098)

Apparently fields are only used by constructors, so no need to keep
them.

Author: Fznamznon

clang/lib/Sema/SemaSYCL.cpp

@@ -2887,7 +2887,6 @@ class SyclKernelBodyCreator : public SyclKernelFieldHandler {
   llvm::SmallVector<std::pair<InitializedEntity, uint64_t>, 8> ArrayInfos;
   VarDecl *KernelObjClone;
   InitializedEntity VarEntity;
-  const CXXRecordDecl *KernelObj;
   llvm::SmallVector<Expr *, 16> MemberExprBases;
   llvm::SmallVector<Expr *, 16> ArrayParamBases;
   FunctionDecl *KernelCallerFunc;
@@ -3419,7 +3418,7 @@ class SyclKernelBodyCreator : public SyclKernelFieldHandler {
         KernelObjClone(createKernelObjClone(S.getASTContext(),
                                             DC.getKernelDecl(), KernelObj)),
         VarEntity(InitializedEntity::InitializeVariable(KernelObjClone)),
-        KernelObj(KernelObj), KernelCallerFunc(KernelCallerFunc),
+        KernelCallerFunc(KernelCallerFunc),
         KernelCallerSrcLoc(KernelCallerFunc->getLocation()),
         IsESIMD(IsSIMDKernel), CallOperator(CallOperator) {
     CollectionInitExprs.push_back(createInitListExpr(KernelObj));
@@ -3624,7 +3623,6 @@ class SyclKernelIntHeaderCreator : public SyclKernelFieldHandler {
   int64_t CurOffset = 0;
   llvm::SmallVector<size_t, 16> ArrayBaseOffsets;
   int StructDepth = 0;
-  bool IsESIMD = false;
 
   // A series of functions to calculate the change in offset based on the type.
   int64_t offsetOf(const FieldDecl *FD, QualType ArgTy) const {
@@ -3656,7 +3654,7 @@ class SyclKernelIntHeaderCreator : public SyclKernelFieldHandler {
   SyclKernelIntHeaderCreator(bool IsESIMD, Sema &S, SYCLIntegrationHeader &H,
                              const CXXRecordDecl *KernelObj, QualType NameType,
                              FunctionDecl *KernelFunc)
-      : SyclKernelFieldHandler(S), Header(H), IsESIMD(IsESIMD) {
+      : SyclKernelFieldHandler(S), Header(H) {
 
     // The header needs to access the kernel object size.
     int64_t ObjSize = SemaRef.getASTContext()