1199:9070 is a bootloader device ID. It is expected to have only one serial function on USB interface #0. No driver juggling is going to change that, ever.
What you might want to ask is why the MC7455 isn’t booting. This is a firmware issue on the MC7455. But the root cause can be anything from hardware errors and NVRAM issues to a simple missing firmware. If you’re lucky, then reinstalling the firmware might fix it. That’s the first thing I would have tried.