Sprinkle EARLY_DRIVER_MODULE around the tree

Mark some buses as BUS_PASS_BUS, and some resources as BUS_PASS_RESOURCE.
This also decouples some resource attachment orderings from being races by
device tree ordering, instead relying on the bus pass to provide the
ordering.

This was originally intended to support multipass suspend/resume, but it's
also needed on PowerMacs when using fdt, as the device tree seems to get
created in reverse of the OFW tree.
Reviewed by: nwhitehorn (long ago)
Differential Revision: https://reviews.freebsd.org/D918