[OpenCL][Sema] Improving formatting
[OpenCL][Sema] Improving formatting

Reformat comment added in r348120 following
review https://reviews.llvm.org/D55136.



git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@348139 91177308-0d34-0410-b5e6-96231b3b80d8

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