[CRYPTO] api: Add async blkcipher type

This patch adds the mid-level interface for asynchronous block ciphers.
It also includes a generic queueing mechanism that can be used by other
asynchronous crypto operations in future.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/Kconfig b/crypto/Kconfig
index 086fcec..a20a3f1 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -16,6 +16,10 @@
 	help
 	  This option provides the API for cryptographic algorithms.
 
+config CRYPTO_ABLKCIPHER
+	tristate
+	select CRYPTO_BLKCIPHER
+
 config CRYPTO_BLKCIPHER
 	tristate
 	select CRYPTO_ALGAPI