pci_setup_device() has saved the PCI revision in the pci_dev
struct since Linux 2.6.23.  Use it.

Cc: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>