Change the dev argument from a full path to just the device

Change the dev argument from a full path to just the device
identification (e.g. isa:0x3f0 or pci0:2:1:0). In libbus,
the device is turned into a path name. For bus_space_map(),
the resource is now specified in a second argument.
Before:
	bus.map('/dev/proto/pci0:2:1:0/pcicfg')
	busdma.tag_create('/dev/proto/pci0:2:1:0/busdma', ...)
Now:
	bus.map('pci0:2:1:0', 'pcicfg')
	busdma.tag_create('pci0:2:1:0', ...)