sunrpc: add hash_cred() function to rpc_authops struct

Currently, a single hash algorithm is used to hash the auth_cred for
the credcache for all rpc_auth types.  Add a hash_cred() function to
the rpc_authops struct to allow a hash function specific to each
auth flavor.
Signed-off-by: Frank Sorenson <sorenson@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

include/linux/sunrpc/auth.h

@@ -131,6 +131,7 @@ struct rpc_authops {
 	struct rpc_auth *	(*create)(struct rpc_auth_create_args *, struct rpc_clnt *);
 	void			(*destroy)(struct rpc_auth *);
 
+	int			(*hash_cred)(struct auth_cred *, unsigned int);
 	struct rpc_cred *	(*lookup_cred)(struct rpc_auth *, struct auth_cred *, int);
 	struct rpc_cred *	(*crcreate)(struct rpc_auth*, struct auth_cred *, int, gfp_t);
 	int			(*list_pseudoflavors)(rpc_authflavor_t *, int);