firewire: force root change when root node is not cycle master capable

[guest-seuros]

Summary

When a FireWire bus resets, all devices negotiate who is the new boss.
when we detect the root node can't be cycle master,
we send a PHY config packet that forces a reelection.

Test Plan

Problem: sometimes a dumb device (like a disk enclosure or a camera) wins the root election,
but it can't actually do the cycle master.

Quick check: plug the iSight into a chain with a FireWire disk,
and the camera stream actually starts instead of silently failing because the disk grabbed root.