No diagnostic for checking reqd_work_group_size and reqd_work_group_size attributes when merging

[smanna12]

// FIXME: We do not have support yet for checking
// reqd_work_group_size and reqd_work_group_size
// attributes when merging, so the test compiles without
// any diagnostic when it shouldn't

[[sycl::reqd_work_group_size(32, 1, 1)]] void f(); // expected-note {{conflicting attribute is here}} now OK
[[sycl::reqd_work_group_size(1, 1, 32)]] void f(); // expected-error{{'reqd_work_group_size' attribute conflicts with 'reqd_work_group_size' attribute}} now OK