No diagnostic for checking reqd_work_group_size and num_simd_work_items attributes when merging

[smanna12]

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

[[sycl::reqd_work_group_size(4, 2, 3)]] void func2(); // expected-note{{conflicting attribute is here}} now OK
[[intel::num_simd_work_items(2)]] void func2(); // expected-error{{'num_simd_work_items' attribute must evenly divide the work-group size for the 'reqd_work_group_size' attribute}} now OK