From: Pavel Roskin <proski@gnu.org>

If I eject IDE CompactFlash card, I get a stack dump from
devfs_remove() because ide/host2/bus0/target0/lun0 doesn't exist.

After del_gendisk() is called from idedisk_cleanup() drive->devfs_name refers
to a non-existent directory and should be erased, so that ide_unregister()
doesn't try to remove that directory again.