powerpc/fsl_pci: Store the pci ctlr device ptr in the pci ctlr struct

The pci controller structure has a provision to store the device structure
pointer of the corresponding platform device. Currently this information is
not stored during fsl pci controller initialization. This information is
required while dealing with iommu groups for pci devices connected to the
fsl pci controller. For the case where the pci devices can't be paritioned,
they would fall under the same device group as the pci controller.

This patch stores the platform device information in the pci controller
structure during initialization.

Signed-off-by: Varun Sethi <Varun.Sethi@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>