[POWERPC] Add "parent" struct device for PCI host bridges

Add a "parent" struct device to our PCI host bridge data structure so that
PCI can be rooted off another device in sysfs.

Note that arch/ppc doesn't use it, only arch/powerpc, though it's available
for both 32 and 64 bits.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

include/asm-powerpc/pci-bridge.h

@@ -25,6 +25,7 @@ struct pci_controller {
 	int node;
 	void *arch_data;
 	struct list_head list_node;
+	struct device *parent;
 
 	int first_busno;
 	int last_busno;