{mb,nb,soc}: Remove references to pci_bus_default_ops()

pci_bus_default_ops() is the default anyway.

Change-Id: I5306d3feea3fc583171d8c865abbe0864b6d9cc6
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/26055
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/quark/chip.c

@@ -130,7 +130,6 @@ static struct device_operations pci_domain_ops = {
 	.read_resources	= pci_domain_read_resources,
 	.set_resources	= pci_domain_set_resources,
 	.scan_bus	= pci_domain_scan_bus,
-	.ops_pci_bus	= pci_bus_default_ops,
 };
 
 static void chip_enable_dev(device_t dev)