[flang] Add more diagnostics to fir.coordinate_of

Add more diagnostics to fir.coordinate_of to provide better checking
that the IR is sane.

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

Reviewed By: PeteSteinfeld

Differential Revision: https://reviews.llvm.org/D128255



Co-authored-by: Eric Schweitz <eschweitz@nvidia.com>