Merging r275935:

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r275935 | arsenm | 2016-07-18 17:35:22 -0700 (Mon, 18 Jul 2016) | 6 lines

AMDGPU/SI: Fix SI scheduler refcount issue

Without this fix, releaseSuccessors when InOrOutBlock is
false could release SUs outside the schedule BasicBlock.

Patch by Axel Davy
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llvm-svn: 276116