[flang] Fix one regression failure related to BIND(C) statement

For BIND(C) statement, two common block with the same name can have the
same bind name. Fix the regression failure by adding this check. Also add
the regression tests.

Co-authored-by: Jean Perier <jperier@nvidia.com>

Reviewed By: clementval

Differential Revision: https://reviews.llvm.org/D127841