[flang] Add bind(C) to buitlin C_PTR

D131585 Adds couple of semantics check for the components of BIND(C)
derived-type. This would raise an error when a component is of C_PTR
type. Add `bind(c)` to the `__builtin_c_ptr` type so the wrong error
is not triggered.

Reviewed By: peixin, jeanPerier

Differential Revision: https://reviews.llvm.org/D132350