PCI: Add pci_wait_for_pending() (refactor pci_wait_for_pending_transaction())

We currently have two instance of this loop which waits for a pending bit
to clear in a status dword.  Generalize the function for future users.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 1084a15..211ce43 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -938,6 +938,7 @@
 void pci_msi_off(struct pci_dev *dev);
 int pci_set_dma_max_seg_size(struct pci_dev *dev, unsigned int size);
 int pci_set_dma_seg_boundary(struct pci_dev *dev, unsigned long mask);
+int pci_wait_for_pending(struct pci_dev *dev, int pos, u16 mask);
 int pci_wait_for_pending_transaction(struct pci_dev *dev);
 int pcix_get_max_mmrbc(struct pci_dev *dev);
 int pcix_get_mmrbc(struct pci_dev *dev);