Thumb2 literal loads use an offset encoding which allows for
negative zero. This fixes parsing and encoding so that #-0
is correctly processed. The parser represents #-0 as INT32_MIN.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188549 91177308-0d34-0410-b5e6-96231b3b80d8