of: pci: add registry of MSI chips

This commit adds a very basic registry of msi_chip structures, so that
an IRQ controller driver can register an msi_chip, and a PCIe host
controller can find it, based on a 'struct device_node'.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>
diff --git a/include/linux/msi.h b/include/linux/msi.h
index 090ddad..b17ead8 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -68,6 +68,8 @@
 struct msi_chip {
 	struct module *owner;
 	struct device *dev;
+	struct device_node *of_node;
+	struct list_head list;
 
 	int (*setup_irq)(struct msi_chip *chip, struct pci_dev *dev,
 			 struct msi_desc *desc);