[PATCH] Clarify wording in the LangRef around !invariant.load

[Sanjoy Das]

> I would actually be fine with more conservative semantics - the load is only invariant with respect to its original uses - because it won't affect optimization in practice.

I was under the impression that one of motivations for invariant loads
was to be able to hoist them out of arbitrary control flow.

Thanks,
-- Sanjoy