vmwgfx: return -EFAULT if copy_to_user fails

copy_to_user() returns the number of bytes remaining to be copied, but
we want to return a negative error code.  This gets copied to user
space.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/vmwgfx/vmwgfx_kms.c

@@ -972,6 +972,7 @@ int vmw_kms_update_layout_ioctl(struct drm_device *dev, void *data,
 	ret = copy_from_user(rects, user_rects, rects_size);
 	if (unlikely(ret != 0)) {
 		DRM_ERROR("Failed to get rects.\n");
+		ret = -EFAULT;
 		goto out_free;
 	}