llvm-readobj: relocAddressLess could potentially lie

On error conditions, relocAddressLess might claim that a value is less
than itself.  Instead, abort llvm-readobj.  No functionality change
intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221872 91177308-0d34-0410-b5e6-96231b3b80d8