[flang] Fix the interface for numerical/logical scalar with VALUE attribute

Programmers may use procedure without BIND(C) attribute to interoperate
with C code. For numerical/logical scalar with VALUE attribute, pass the
argument by value so that the behavior is consistent with gfortran or
nvfortran. The argument with the OPTIONAL attribute cannot be passed by
value since the actual argument may be absent.

For the derived type, pass-by-value is not supported yet, so pass the
argument by reference for now.

Reviewed By: jeanPerier

Differential Revision: https://reviews.llvm.org/D136260