[CUDA] Fix flush-denormals.cu test so that it checks what it intends to CHECK.
[CUDA] Fix flush-denormals.cu test so that it checks what it intends to CHECK.

FileCheck does not evaluate plain CHECKs if you pass -check-prefix; you
have to ask for it explicitly.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@269000 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang