This resolves a number of issues that came to light when working
on chipc-attached PMU support:
- Added missing bhnd_nexus bhnd_bus_deactivate_resource implementation.
- Delete all chipc children on attachment failure.
- Drop a CHIPC_UNLOCK() accidentally left behind after lifting synchronization into the chipc region refcounting API.
- Fix re-allocation of chipc resources. Previously, the resource ID was reset to -1 on release, preventing later re-allocation.