vfio/type1: Remove pid_namespace.h include

Using has_capability() rather than ns_capable(), we're no longer using
this header.

Cc: Jike Song <jike.song@intel.com>
Cc: Kirti Wankhede <kwankhede@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/vfio_iommu_type1.c

@@ -36,7 +36,6 @@
 #include <linux/uaccess.h>
 #include <linux/vfio.h>
 #include <linux/workqueue.h>
-#include <linux/pid_namespace.h>
 #include <linux/mdev.h>
 #include <linux/notifier.h>