Kernel panic via cleanup of uninitialized module state

Cleanup errors in Linux 5.12 VMBus allow local users to panic the kernel by unloading the module in a non-nested root partition. The hv_acpi_init() function reports success without initializing VMBus in this configuration, but module exit cleans up uninitialized resources and causes memory faults. Triggering the failure requires privileged module-unload access on a non-nested Hyper-V root partition; the documented consequence is a kernel crash.