[patch] Remove the 's' DataLayout specification

[Rafael Espíndola]

> This is fine with me in principle, assuming it doesn’t change any interesting behavior :-).

It preserves behavior for any in tree target. An out of tree target
using 's' would just have to create a trivial getByValTypeAlignment
like the one the patch adds for AArch64:

unsigned FooTargetLowering::getByValTypeAlignment(Type *Ty) const {
  return the_value_that_was_in_s;
}

If that is ok I will apply the patch and send an email to llvmdev
about the change.

Cheers,
Rafael