udmabuf: Add missing compact_ioctl

Make sure we can use this on mixed systems.
Signed-off-by: Kristian H. Kristensen <hoegsberg@google.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20200903181652.432067-1-hoegsberg@google.comSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/dma-buf/udmabuf.c

@@ -308,6 +308,9 @@ static long udmabuf_ioctl(struct file *filp, unsigned int ioctl,
 static const struct file_operations udmabuf_fops = {
 	.owner		= THIS_MODULE,
 	.unlocked_ioctl = udmabuf_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl   = udmabuf_ioctl,
+#endif
 };
 
 static struct miscdevice udmabuf_misc = {