Merging r295512:

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r295512 | matze | 2017-02-17 15:15:03 -0800 (Fri, 17 Feb 2017) | 8 lines

AArch64LoadStoreOptimizer: Correctly clear kill flags

When promoting the Load of a Store-Load pair to a COPY all kill flags
between the store and the load need to be cleared.

rdar://30402435

Differential Revision: https://reviews.llvm.org/D30110
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llvm-svn: 295744