This seems like redundant leftovers from r142288 - exposing
TargetData::parseSpecifier to LLParser - which got reverted. Removes
redunant td != NULL checks in parseSpecifier, and simplifies the
interface to parseSpecifier and init.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167924 91177308-0d34-0410-b5e6-96231b3b80d8