[SPARC64]: Refine Sabre wsync logic.

It is only needed when there is a PCI-PCI bridge sitting
between the device and the PCI host controller which is
not a Simba APB bridge.

Add logic to handle two special cases:

1) device behind EBUS, which sits on PCI
2) PCI controller interrupts

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