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

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

Depends on D150224

Reviewed By: vzakhari

Differential Revision: https://reviews.llvm.org/D150225