qmi-codegen: ensure fields with prerequisites are handled after the prerequisites
qmi-codegen: ensure fields with prerequisites are handled after the prerequisites

Currently we only support:
   * fields without prerequisites and which are not prerequisite of another field.
   * fields without prerequisites and which are prerequisite of another field.
   * fields with 1 prerequisite and which are not prerequisite of another field

We'll add more support whenever needed.

roland-wilhelm/libqmi,roland-wilhelm/libqmi,roland-wilhelm/libqmi,roland-wilhelm/libqmi