firewire: Implement suspend/resume PCI driver hooks.

It's a low-impact design, that just makes suspend/resume look like
a bus reset to the upper level drivers, but it should be sufficient.

Signed-off-by: Kristian Høgsberg <krh@redhat.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>