[ELF] - Remove dead code from LinkerScript::assignOffsets(). NFC-ihope.

Some parts of the code changed are a bit old. I found traces in 2016.

Initiall commits has test cases and perhaps reasonable comments.
For example, we had segfaults earlier and had the code to fix them.

Now, in 2018, I think it is excessive to have these parts, because
we do not have segfaults and our code was changed a lot (softly saying).

I reviewed the current sources and I think that at this point of the
execution flow, we should never face with
the conditions checked and so I removing them in this patch.

This helps to cleanup the code.

llvm-svn: 339003