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: NGilad Ben-Yossef <gilad@benyossef.com>
Suggested-by: NStephan Mueller <smueller@chronox.de>
Acked-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

crypto/Kconfig

@@ -430,11 +430,14 @@ config CRYPTO_CTS
 	help
 	  CTS: Cipher Text Stealing
 	  This is the Cipher Text Stealing mode as described by
-	  Section 8 of rfc2040 and referenced by rfc3962.
-	  (rfc3962 includes errata information in its Appendix A)
+	  Section 8 of rfc2040 and referenced by rfc3962
+	  (rfc3962 includes errata information in its Appendix A) or
+	  CBC-CS3 as defined by NIST in Sp800-38A addendum from Oct 2010.
 	  This mode is required for Kerberos gss mechanism support
 	  for AES encryption.
 
+	  See: https://csrc.nist.gov/publications/detail/sp/800-38a/addendum/final
+
 config CRYPTO_ECB
 	tristate "ECB support"
 	select CRYPTO_BLKCIPHER