Remove LoadCommandInfo now that we always have a pointer to the command.

LoadCommandInfo was needed to keep a command and its offset in the file. Now
that we always have a pointer to the command, we don't need the offset.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178991 91177308-0d34-0410-b5e6-96231b3b80d8