PCI: Include pci.h for struct pci_ops definition

struct pci_ecam_ops embeds a struct pci_ops.  Explicitly request the
definition for struct pci_ops, otherwise gcc might complain:

  include/linux/pci-ecam.h:29:19: error: field 'pci_ops' has incomplete type

Signed-off-by: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>