Removing potentially error-prone fallthrough. NFC
Removing potentially error-prone fallthrough. NFC

This fallthrough if other cases are added between fabs and default
could cause fabs to fall to the next case resulting in a bug.
Better getting rid of it immediately just to be sure.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@292003 91177308-0d34-0410-b5e6-96231b3b80d8

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