[flang] Avoid infinite recursion in common block check

Don't call CheckCommonBlockDerivedType() recursively if the
derived type symbol is the same symbol that is already being
processed. This can happen when a component is a pointer of the
same type as its parent component, for instance.

Fixes #60230

Reviewed By: klausler

Differential Revision: https://reviews.llvm.org/D143211