crypto: cts - document NIST standard status

cts(cbc(aes)) as used in the kernel has been added to NIST
standard as CBC-CS3. Document it as such.

Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Suggested-by: Stephan Mueller <smueller@chronox.de>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>