crypto: scatterwalk - Add missing sg_init_table to scatterwalk_ffwd

We need to call sg_init_table as otherwise the first entry may
inadvertently become the last.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/scatterwalk.c

@@ -158,6 +158,7 @@ struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
 		src = sg_next(src);
 	}
 
+	sg_init_table(dst, 2);
 	sg_set_page(dst, sg_page(src), src->length - len, src->offset + len);
 	scatterwalk_crypto_chain(dst, sg_next(src), 0, 2);