[Clang] Fix defaulted equality operator so that it does not attempt to compare unnamed bit-fields

If we look at class.bit p2 it tells us that that unnamed bit-fields are not
members and class.compare.default p5 tells us that we should only compare
non-static data members of the class.

This fixes: https://github.com/llvm/llvm-project/issues/61335 and https://github.com/llvm/llvm-project/issues/61417

Differential Revision: https://reviews.llvm.org/D146329