powerpc/fsl-pci: Unify pci/pcie initialization code

We unified the Freescale pci/pcie initialization by changing the fsl_pci
to a platform driver. In previous PCI code architecture the initialization
routine is called at board_setup_arch stage. Now the initialization is done
in probe function which is architectural better. Also It's convenient for
adding PM support for PCI controller in later patch.

Now we registered pci controllers as platform devices. So we combine two
initialization code as one platform driver.

Signed-off-by: Jia Hongtao <B38951@freescale.com>
Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: Chunhe Lan <Chunhe.Lan@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>