[flang][NFC] Add TODOs for KIND = 2

Add TODO for KIND=2 so the user is notified correctly.

This patch is part of the upstreaming effort from fir-dev branch.

Reviewed By: jeanPerier, PeteSteinfeld

Differential Revision: https://reviews.llvm.org/D127619



Co-authored-by: Peter Steinfeld <psteinfeld@nvidia.com>