Added the following domain attributes for the FSL PAMU driver:
1. Added new iommu stash attribute, which allows setting of the
LIODN specific stash id parameter through IOMMU API.
2. Added an attribute for enabling/disabling DMA to a particular
memory window.
3. Added domain attribute to chec
swap_pci_ref function is used by the IOMMU API code for swapping pci device
pointers, while determining the iommu group for the device.
Currently this function was being implemented for different IOMMU drivers.
This patch moves the function to pci.h so that the implementation can be
shared across v
