drm: cast handle to a pointer to avoid warning

Andrew reported a warning on this line, just case to void *.

Signed-off-by: Dave Airlie <airlied@linux.ie>
diff --git a/drivers/char/drm/drm_bufs.c b/drivers/char/drm/drm_bufs.c
index bb989cc..e3d372a 100644
--- a/drivers/char/drm/drm_bufs.c
+++ b/drivers/char/drm/drm_bufs.c
@@ -309,7 +309,7 @@
 
 	if (copy_to_user(argp, maplist->map, sizeof(drm_map_t)))
 		return -EFAULT;
-	if (put_user(maplist->user_token, &argp->handle))
+	if (put_user((void *)maplist->user_token, &argp->handle))
 		return -EFAULT;
 	return 0;
 }