PCI: PCIe portdrv: Use driver data to simplify code

PCI Express port driver extension, as defined by struct
pcie_port_device_ext in portdrv.h, is allocated and initialized, but
never used (it also is never freed).  Extend it to hold the PCI Express
port type as well as the port interrupt mode, change its name and use it
to simplify the code in portdrv_core.c .

Additionally, remove the redundant interrupt_mode member of struct
pcie_device defined in include/linux/pcieport_if.h .

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>