staging: vt6656: Add comment for locks

This patch fixes the checkpatch.pl warnings like:
- CHECK: spinlock_t definition without comment

Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/c6a5ef8e7704b488c54145b09ac44bd4880c13b4.1645477326.git.philipp.g.hortmann@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>