powerpc/85xx: Add host-pci(e) bridge only for RC

FSL PCIe controller can act as agent(EP) or host(RC).  Under Agent(EP) mode
the controller will be configured by the host system.  So its not required
to be registered with the PCI(e) sub-system. We only register the
controller if its configured in host(RC) mode.

Signed-off-by: Vivek Mahajan <vivek.mahajan@freescale.com>
Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>