set power state of firewire host during suspend

Put firewire host controller in PCI Dx state for system suspend.
(I was not able to measure any power savings, but it sounds like right
thing to do, anyway.)

Signed-off-by: Pavel Machek <pavel@suse.cz>
Update by stefanr:  Shuffle with existing PPC_PMAC code.  Set power
state in the resume hook too.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>