[TableGen] Fix std::array initializer to avoid warnings with older tool chains. NFC
[TableGen] Fix std::array initializer to avoid warnings with older tool chains. NFC

A std::array is implemented as a template with an array inside a struct.
Older versions of clang, like 3.6, require an extra set of curly braces
around std::array initializations to avoid warnings.

The C++ language was changed regarding this by CWG 1270. So more modern
tool chains does not complain even if leaving out one level of braces.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@362360 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm