Add a lemma to ease the proof of Hacl.Streaming.Functor.update_small
Add a lemma to ease the proof of Hacl.Streaming.Functor.update_small

mitls/hacl-star,mitls/hacl-star,mitls/hacl-star,mitls/hacl-star,mitls/hacl-star,mitls/hacl-star,mitls/hacl-star,mitls/hacl-star,mitls/hacl-star