firewire: fw-ohci: ignore failure of pci_set_power_state (fix suspend regression)

Fixes (papers over) "Sleep problems with kernels >= 2.6.21 on powerpc",
http://lkml.org/lkml/2007/8/25/155.  The issue is that the FireWire
controller's pci_dev.current_state of iBook G3 and presumably older
PowerBooks is still in PCI_UNKNOWN instead of PCI_D0 when the firewire
driver's .suspend method is called.

Like it was suggested earlier in http://lkml.org/lkml/2006/10/24/13, we
do not fail .suspend anymore if pci_set_power_state failed.

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