Now that we have converted all bus specific routines to replaceable, we
can move the PCI specific codes into a separate file.

Changes-licensed-under: ISC
Signed-off-by: NGabor Juhos <juhosg@openwrt.org>
Signed-off-by: NImre Kaloz <kaloz@openwrt.org>
Tested-by: NPavel Roskin <proski@gnu.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>