[openmp] Remove clause from OMPKinds.def and use OMP.td info

Remove the OpenMP clause information from the OMPKinds.def file and use the
information from the new OMP.td file. There is now a single source of truth for the
directives and clauses.

To avoid generate lots of specific small code from tablegen, the macros previously
used in OMPKinds.def are generated almost as identical. This can be polished and
possibly removed in a further patch.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D92955