ofw_bus_gen_get_*() for providing the ofw_bus KOBJ interface in order
to reduce code duplication.
- While here sync the various sparc64 bus drivers a bit (handle failure
to attach a child gracefully instead of panicing, move the printing
of child resources common to bus_print_child() and bus_probe_nomatch()
implementations of a bus into a <bus>_print_res() function, ...) and
fix some minor bugs and nits (plug memory leaks present when attaching
a bus or child device fails, remove unused struct members, ...).
Additional testing by: kris (central(4) and fhc(4))
a1a074b6b3