Revert "powerpc/pci: Remove unused struct pci_dn.pcidev field"

This commit removed the pcidev field from struct pci_dn as it was no
longer in use by the kernel. However to support finding the
association of Nvlink devices to GPU devices from the device-tree this
field is required.

This reverts commit 250c7b277c65 ("powerpc/pci: Remove unused struct
pci_dn.pcidev field").

Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/include/asm/pci-bridge.h b/arch/powerpc/include/asm/pci-bridge.h
index 37fc535..54843ca 100644
--- a/arch/powerpc/include/asm/pci-bridge.h
+++ b/arch/powerpc/include/asm/pci-bridge.h
@@ -205,6 +205,7 @@
 
 	int	pci_ext_config_space;	/* for pci devices */
 
+	struct	pci_dev *pcidev;	/* back-pointer to the pci device */
 #ifdef CONFIG_EEH
 	struct eeh_dev *edev;		/* eeh device */
 #endif