sparc64: Fix OOPS in psycho_pcierr_intr_other().

We no longer put the top-level PCI controller device into the
PCI layer device list.  So pbm->pci_bus->self is always NULL.

Therefore, use direct PCI config space accesses to get at
the PCI controller's PCI_STATUS register.

Tested by Meelis Roos.

Signed-off-by: David S. Miller <davem@davemloft.net>