PCI: Fix warnings when CONFIG_DMI unset

PCI: Fix warnings when CONFIG_DMI unset

This patch fixes the below warnings introduced by the commit
911e1c9b05a8e3559a7aa89083930700a0b9e7ee ("PCI:
export SMBIOS provided firmware instance and label to sysfs").

drivers/pci/pci.h: In function ‘pci_create_firmware_label_files’:
drivers/pci/pci.h:16: warning: ‘return’ with a value, in function returning void
drivers/pci/pci.h: In function ‘pci_remove_firmware_label_files’:
drivers/pci/pci.h:18: warning: ‘return’ with a value, in function returning void

The warnings are seen because of the below code, doing a retun 0
from the functions 'pci_create_firmware_label_files' and
'pci_remove_firmware_label_files' defined as void.

+#ifndef CONFIG_DMI
+static inline void pci_create_firmware_label_files(struct pci_dev *pdev)
+{ return 0; }
+static inline void pci_remove_firmware_label_files(struct pci_dev *pdev)
+{ return 0; }

Signed-off-by: Narendra K <narendra_k@dell.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>