crypto: nhpoly1305 - add NHPoly1305 support

Add a generic implementation of NHPoly1305, an ε-almost-∆-universal hash
function used in the Adiantum encryption mode.

CONFIG_NHPOLY1305 is not selectable by itself since there won't be any
real reason to enable it without also enabling Adiantum support.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/Kconfig b/crypto/Kconfig
index 4431c0d..eaeb8a9 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -496,6 +496,11 @@
 	  Support for key wrapping (NIST SP800-38F / RFC3394) without
 	  padding.
 
+config CRYPTO_NHPOLY1305
+	tristate
+	select CRYPTO_HASH
+	select CRYPTO_POLY1305
+
 comment "Hash modes"
 
 config CRYPTO_CMAC