Specify complete triple for fp128 tests.

This avoids FileCheck failing over different comment characters in
assembly (notably powerpc64 on Linux vs Darwin) and should fix David's
build-bot.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171886 91177308-0d34-0410-b5e6-96231b3b80d8