PCI: pciehp: remove pci_dev field

Since we have a pointer to pcie_device in struct controller, we don't
need a pointer to pci_dev.

Acked-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>