Autotension - doesn't compile

FYI, Brad referred that the auto-tension did not compile in Libbarrett-RT_PREEMPT branch. That's why he removed the auto-tension from the CmakeLists.txt.

However, I did not see any error coming from auto-tension while compiling Libbarrett-RT_PREEMPT in Ubuntu 18.04 (kernel-4.18.16-rt9).