CIFS: Add capability to decrypt big read responses

Allow to decrypt transformed packets that are bigger than the big
buffer size. In particular it is used for read responses that can
only exceed the big buffer size.

Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>

fs/cifs/cifsproto.h

@@ -77,6 +77,7 @@ extern void cifs_delete_mid(struct mid_q_entry *mid);
 extern void cifs_wake_up_task(struct mid_q_entry *mid);
 extern int cifs_handle_standard(struct TCP_Server_Info *server,
 				struct mid_q_entry *mid);
+extern int cifs_discard_remaining_data(struct TCP_Server_Info *server);
 extern int cifs_call_async(struct TCP_Server_Info *server,
 			struct smb_rqst *rqst,
 			mid_receive_t *receive, mid_callback_t *callback,