PCI ops: MMCONF_SUPPORT_DEFAULT is required

Doing PCI config operations via MMIO window by default is a
requirement, if supported by the platform. This means chipset
or CPU code must enable MMCONF operations early in bootblock
already, or before platform-specific romstage entry.

Platforms are allowed to have NO_MMCONF_SUPPORT only in the
case it is actually not implemented in the silicon.

Change-Id: Id4d9029dec2fe195f09373320de800fcdf88c15d
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/17693
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/device/pci_ops.c

@@ -22,11 +22,10 @@
 
 const struct pci_bus_operations *pci_bus_default_ops(device_t dev)
 {
-#if CONFIG_MMCONF_SUPPORT_DEFAULT
+	if (IS_ENABLED(CONFIG_NO_MMCONF_SUPPORT))
+		return &pci_cf8_conf1;
+
 	return &pci_ops_mmconf;
-#else
-	return &pci_cf8_conf1;
-#endif
 }
 
 static const struct pci_bus_operations *pci_bus_ops(struct bus *bus, struct device *dev)