firewire: fw-ohci: switch on bus power after resume on PPC PMac

The platform feature calls in the suspend method switched off cable
power, but the calls in the resume method did not switch it back on.

Add the necessary feature call to .resume.  Also add the corresponding
call to .suspend to make .suspend's behavior explicitly the same on all
PMacs.

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