[NFC][SYCL] Remove unnecessary if condition (#2585)

This if condition duplicates logic of outer if.

Author: Fznamznon

clang/lib/Sema/SemaDeclAttr.cpp

@@ -8310,10 +8310,8 @@ void Sema::ProcessDeclAttributeList(Scope *S, Decl *D,
       Diag(D->getLocation(), diag::err_opencl_kernel_attr) << A;
       D->setInvalidDecl();
     } else if (const auto *A = D->getAttr<IntelReqdSubGroupSizeAttr>()) {
-      if (!getLangOpts().SYCLIsDevice) {
-        Diag(D->getLocation(), diag::err_opencl_kernel_attr) << A;
-        D->setInvalidDecl();
-      }
+      Diag(D->getLocation(), diag::err_opencl_kernel_attr) << A;
+      D->setInvalidDecl();
     } else if (!D->hasAttr<CUDAGlobalAttr>()) {
       if (const auto *A = D->getAttr<AMDGPUFlatWorkGroupSizeAttr>()) {
         Diag(D->getLocation(), diag::err_attribute_wrong_decl_type)