pci: fix compilation when CONFIG_PCI_MSI=n

drivers/pci/pci.c:2277: error: redefinition of ‘pci_msi_off’
include/linux/pci.h:786: note: previous definition of ‘pci_msi_off’ was here

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 drivers/pci/pci.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2266,6 +2266,7 @@ pci_intx(struct pci_dev *pdev, int enabl
 	}
 }
 
+#ifdef CONFIG_PCI_MSI
 /**
  * pci_msi_off - disables any msi or msix capabilities
  * @dev: the PCI device to operate on
@@ -2293,6 +2294,7 @@ void pci_msi_off(struct pci_dev *dev)
 	}
 }
 EXPORT_SYMBOL_GPL(pci_msi_off);
+#endif
 
 #ifndef HAVE_ARCH_PCI_SET_DMA_MAX_SEGMENT_SIZE
 int pci_set_dma_max_seg_size(struct pci_dev *dev, unsigned int size)