[media] v4l2-ioctl: fix incorrect error code if VIDIOC_DBG_G/S_REGISTER are unsupported

The ioctls VIDIOC_DBG_S_REGISTER and VIDIOC_DBG_G_REGISTER should return -EINVAL
if the driver didn't implement them. Currently they return -EPERM if called as
non-root user. However, this check should only be done if the driver actually
implemented these ioctls. Otherwise, just return -EINVAL as we do with all
unimplemented ioctls.

This bug make the v4l2-compliance test suite fail.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/v4l2-ioctl.c

@@ -1659,20 +1659,24 @@ static long __video_do_ioctl(struct file *file,
 	{
 		struct v4l2_dbg_register *p = arg;
 
-		if (!capable(CAP_SYS_ADMIN))
-			ret = -EPERM;
-		else if (ops->vidioc_g_register)
-			ret = ops->vidioc_g_register(file, fh, p);
+		if (ops->vidioc_g_register) {
+			if (!capable(CAP_SYS_ADMIN))
+				ret = -EPERM;
+			else
+				ret = ops->vidioc_g_register(file, fh, p);
+		}
 		break;
 	}
 	case VIDIOC_DBG_S_REGISTER:
 	{
 		struct v4l2_dbg_register *p = arg;
 
-		if (!capable(CAP_SYS_ADMIN))
-			ret = -EPERM;
-		else if (ops->vidioc_s_register)
-			ret = ops->vidioc_s_register(file, fh, p);
+		if (ops->vidioc_s_register) {
+			if (!capable(CAP_SYS_ADMIN))
+				ret = -EPERM;
+			else
+				ret = ops->vidioc_s_register(file, fh, p);
+		}
 		break;
 	}
 #endif