[PATCH] [Power] Add a new feature flag for support of the sync instruction

[Alex Rosenberg]

601 and others had sync.

It's somewhat bizarre to me to define new patterns and features to handle something that encodes to the same bit patterns.

I always assumed "generic" was for the purposes of generating code that ran on the maximum set of hardware and was scheduled in a way to do as well as possible without being specific. More or less, the kind of code that would be used by Mac developers.

http://reviews.llvm.org/D5316