vfio/ccw: Change pa_pfn list to pa_iova list

vfio/ccw: Change pa_pfn list to pa_iova list

The vfio_ccw_cp code maintains both iova and its PFN list because the
vfio_pin/unpin_pages API wanted pfn list. Since vfio_pin/unpin_pages()
now accept "iova", change to maintain only pa_iova list and rename all
"pfn_array" strings to "page_array", so as to simplify the code.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Tested-by: Eric Farman <farman@linux.ibm.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Link: https://lore.kernel.org/r/20220723020256.30081-8-nicolinc@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>