firewire: ohci: Change module_pci_driver to module_init/module_exit

This is a prerequisite to allocate a per driver self_id workqueue.
This reverts the ohci.c part of patch
fe2af11c.

Signed-off-by: Stephan Gatzka <stephan.gatzka@gmail.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>