AMDGPU: Remove GCCBuiltin from intrinsics that need mangling
AMDGPU: Remove GCCBuiltin from intrinsics that need mangling

If the intrinsic is overloaded and works on multiple types,
it cannot resolve to a single corresponding builtin and requires
handling in clang. This just causes crashes now.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@258559 91177308-0d34-0410-b5e6-96231b3b80d8

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