[Flang] Use specific symbol rather than generic symbol as procInterface to...

[Flang] Use specific symbol rather than generic symbol as procInterface to declare procedure pointer. (#80738)

Flang crashes when lowering the type of `p1` with the following code.
The problem is when it sets up the `procInterface`, it uses the generic
symbol `int`, not the specific `int`. This PR is to correct that.

```
  INTERFACE Int
    integer FUNCTION Int(arg)
      integer :: arg
    END FUNCTION
  END INTERFACE

  integer :: res
  procedure(int), pointer :: p1
  p1 => int
  res = p1(4)
  end
  ```