[mlir][openacc] Cleanup acc.parallel from old data clause operands

[mlir][openacc] Cleanup acc.parallel from old data clause operands

Remove old clause operands from acc.parallel operation since
the new dataOperands is now in place.
private, firstprivate and reductions will receive some redesign but are
not part of the new dataOperands.

Reviewed By: razvanlupusoru

Differential Revision: https://reviews.llvm.org/D150207