NAME
driver_register - register driver with bus
SYNOPSIS
int driver_register (struct device_driver * drv);
ARGUMENTS
drv driver to register
DESCRIPTION
We pass off most of the work to the bus_add_driver call, since most of
the things we have to do deal with the bus structures.
The one interesting aspect is that we setup drv->unloaded as a
completion that gets complete when the driver reference count reaches
0.