[CRYPTO] api: Add aead crypto type

This patch adds crypto_aead which is the interface for AEAD
(Authenticated Encryption with Associated Data) algorithms.

AEAD algorithms perform authentication and encryption in one
step.  Traditionally users (such as IPsec) would use two
different crypto algorithms to perform these.  With AEAD
this comes down to one algorithm and one operation.

Of course if traditional algorithms were used we'd still
be doing two operations underneath.  However, real AEAD
algorithms may allow the underlying operations to be
optimised as well.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/Kconfig b/crypto/Kconfig
index 981497c..f42bc77 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -28,6 +28,10 @@
 	tristate
 	select CRYPTO_BLKCIPHER
 
+config CRYPTO_AEAD
+	tristate
+	select CRYPTO_ALGAPI
+
 config CRYPTO_BLKCIPHER
 	tristate
 	select CRYPTO_ALGAPI