s390/cio: Fix how vfio-ccw checks pinned pages

We have two nested loops to check the entries within the pfn_array_table
arrays.  But we mistakenly use the outer array as an index in our check,
and completely ignore the indexing performed by the inner loop.

Cc: stable@vger.kernel.org
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Message-Id: <20181002010235.42483-1-farman@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>