powerpc: struct device - replace bus_id with dev_name(), dev_set_name()

Acked-by: Geoff Levand <geoffrey.levand@am.sony.com>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>