get rid of redundant _smr_ prefix/infix in ThreadSMRSupport stuff

Stefan K code review comment on the fix for:

JDK-8191789 migrate more Thread-SMR stuff from thread.[ch]pp -> threadSMR.[ch]pp

>>> ========================================================================
>>> http://cr.openjdk.java.net/~dcubed/8191789-webrev/jdk10-0/src/hotspot/share/runtime/threadSMR.hpp.udiff.html
>>>
>>> Now that you have moved all these functions and variables to a class named ThreadsSMRSupport maybe you want to consider getting rid of the redundant _smr_ prefix/infix?
>>
>> I thought about that, but it made the sanity checking phase much more
>> difficult because of the noise level in the diffs. What I could do is
>> make that change as the last patch before qfold and qfinish...
>>
>
> It makes sense to me to not change it while moving the files. I think
> its better to push that change as a separate RFE.

Okay. I'll take it on as a separate changeset.