PCI: Export MSI message relevant functions

The patch exports 2 MSI message relevant functions, which will be
used by VFIO PCI driver. The VFIO PCI driver would be built as
a module.
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/pci/msi.c

@@ -312,6 +312,7 @@ void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg)
 
 	__get_cached_msi_msg(entry, msg);
 }
+EXPORT_SYMBOL_GPL(get_cached_msi_msg);
 
 void __write_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
 {
@@ -356,6 +357,7 @@ void write_msi_msg(unsigned int irq, struct msi_msg *msg)
 
 	__write_msi_msg(entry, msg);
 }
+EXPORT_SYMBOL_GPL(write_msi_msg);
 
 static void free_msi_irqs(struct pci_dev *dev)
 {