vfio: Include vfio.h in installed headers

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index d9a7544..fa21760 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -391,6 +391,7 @@
 header-y += v4l2-mediabus.h
 header-y += v4l2-subdev.h
 header-y += veth.h
+header-y += vfio.h
 header-y += vhost.h
 header-y += videodev2.h
 header-y += virtio_9p.h