- pci_disable_device() added in rr_remove_one() to balance
   pci_enable_device() in rr_init_one()
 - rr_timer() and rr_close() are leaking pci_map'ed memory: make them
   use rr_raz_{rx/tx}
 - error exiting path in rr_open() was balancing pci_alloc_consistent()
   with kfree().