After discussion in D93482 we found that the some of the clauses were not
following the common OmpClause convention.
The benefits of using OmpClause:
- Functionalities from structure checker are mostly aligned to work with llvm::omp::Clause.
- The unparsing as well can take advantage.
- Homogeneity with OpenACC and rest of the clauses in OpenMP.
- Could even generate the parser with TableGen, when there is homogeneity.
- It becomes confusing when to use flangClass and flangClassValue inside TableGen, if incase we generate parser using TableGen we could have only a single let expression.
This patch makes OmpDistScheduleClause clause part of OmpClause.
The unparse function for OmpDistScheduleClause is adapted since the keyword
and parenthesis are issued by the corresponding unparse function for