Use PCI_DEVFN() where appropriate.
The resulted stripped binary remains same
with/without thie patch.

Cc: Huacai Chen <zltjiangshi@gmail.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: NIsaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>