By Vesa's DP 1.2 Spec this counter has 4 bits [3:0].
This mask is wrong since when the counter was introduced by myself
on commit ad9dc91b6e21266bfc6f466db4b95e10211f31ee
Author: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Date: Tue Sep 16 19:18:12 2014 -0400