Add support for key derivation cipher operations

Adds a crypto sub-provider for key derivation operations.

Signed-off-by: Julian Hall <julian.hall@arm.com>
Change-Id: I16db22df273151c72d618724331b8cf22e770580
diff --git a/protocols/service/crypto/packed-c/cipher.h b/protocols/service/crypto/packed-c/cipher.h
index 72cd427..48fb470 100644
--- a/protocols/service/crypto/packed-c/cipher.h
+++ b/protocols/service/crypto/packed-c/cipher.h
@@ -9,13 +9,10 @@
 #include <stdint.h>
 
 /**
- * Cipher operations on arbitrary sized data involve three operations,
- * a setup, called once, an update called 1..* times and a finish
- * to finalise theh hash operation.  Operations may be aborted
- * using the abort operation.
+ * Protocol definitions for symmetric cipher operations
+ * using the packed-c serialization.
  */
 
-
 /****************************************
  * cipher_setup operation definition (encrypt or decrypt)
  */