* Serialize operations in acpi_video_bind_outputs(), acpi_video_detach(),
acpi_video_notify_handler(), acpi_video_power_profile(), and the sysctls.
The main goal is to protect the shared device list and prevent conflicting
settings.
* Add assertions that the sx lock is held in the leaf functions.
FOREACH_SAFE. Remove bad cast of retp and instead use an additional
arg to pass back the number of valid outputs. Use the package convenience
functions for parsing packages.
left around after the PCI probe, acpi_video stopped attaching because while
it was an acpi child device, it really is a PCI device. Fix this by making
it a PCI child.
* Remove non-handle ivars accesses since child busses only implement
acpi_get_handle().
* Access the acpi softc directly through the devclass instead of through
the implied parent.
* Clean up a potential panic on unload by freeing the sysctl context before
storing NULL in the OID.
Found by: marks
