crypto: aead - Add common IV generation code

This patch adds some common IV generation code currently duplicated
by seqiv and echainiv.  For example, the setkey and setauthsize
functions are completely identical.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

include/crypto/internal/geniv.h

@@ -0,0 +1,24 @@
+/*
+ * geniv: IV generation
+ *
+ * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ */
+
+#ifndef _CRYPTO_INTERNAL_GENIV_H
+#define _CRYPTO_INTERNAL_GENIV_H
+
+#include <crypto/internal/aead.h>
+#include <linux/spinlock.h>
+
+struct aead_geniv_ctx {
+	spinlock_t lock;
+	struct crypto_aead *child;
+};
+
+#endif	/* _CRYPTO_INTERNAL_GENIV_H */