Add support for PCI-E 5.0 GT/s in max_bus_speed and cur_bus_speed.
Reviewed-by: NMatthew Wilcox <matthew@wil.cx>
Signed-off-by: NKenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>