crypto: lrw - fix rebase error after out of bounds fix

Due to an unfortunate interaction between commit fbe1a850
("crypto: lrw - Fix out-of bounds access on counter overflow") and
commit c778f96b ("crypto: lrw - Optimize tweak computation"),
we ended up with a version of next_index() that always returns 127.

Fixes: c778f96b ("crypto: lrw - Optimize tweak computation")
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>