Add devprops interfaces.
Add devprops implementation.
Add locator properites in config_attach(), add a "cd-name" property to the
rest of the locators, and always allocate a combined device+softc.
Implement dev_mdgetprop().
Support probing and attaching with device properties too.
Probe and attach through devprops.
Match and attach through devprops.
sbus_setup_attach_args() needs to return a struct device pointer now.
Add dev_dumprops() for debug and make dev_mdgetprop() conditional.
Use DEV_PRIVATE() and distinguish between the softc and the device struct.
Convert to support attachment through devprops as well.
Attach through devprops instead of aux.