Revert "Change RelaxELFRelocations for llc."

This reverts commit r273019.

From email I sent to list:
> I don't think this makes sense. Either the linker you're using supports
> this feature, or it doesn't. Having it enabled for llc if your linker
> doesn't support it is not fun.
>
> Further note that this also affects basically all other code using llvm
> libraries -- other than Clang, which explicitly sets it back to false by
> default, unless you set the ENABLE_X86_RELAX_RELOCATIONS cmake flag to
> true.
>
> If you want to enable the relax mode across all llvm tools in some
> circumstances, I think it should be via moving the cmake flag from clang
> down into llvm.
>
> I'm going to revert this commit, since I both think it intrinsically
> doesn't make sense to do this, and because it's breaking some of our
> tools.

llvm-svn: 273245