crypto: caam - fix copy of next buffer for xcbc and cmac

Fix a side effect of adding xcbc support, when the next_buffer is not
copied.
The issue occurs, when there is stored from previous state a blocksize
buffer and received, a less than blocksize, from user. In this case, the
nents for req->src is 0, and the next_buffer is not copied.
An example is:
{
	.tap	= { 17, 15, 8 },
	.psize	= 40,
	.np	= 3,
	.ksize	= 16,
}

Fixes: 12b8567 ("crypto: caam - add support for xcbc(aes)")
Signed-off-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Reviewed-by: Horia Geantă <horia.geanta@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/caam/caamhash.c

@@ -865,19 +865,18 @@ static int ahash_update_ctx(struct ahash_request *req)
 		if (ret)
 			goto unmap_ctx;
 
-		if (mapped_nents) {
+		if (mapped_nents)
 			sg_to_sec4_sg_last(req->src, mapped_nents,
 					   edesc->sec4_sg + sec4_sg_src_index,
 					   0);
-			if (*next_buflen)
-				scatterwalk_map_and_copy(next_buf, req->src,
-							 to_hash - *buflen,
-							 *next_buflen, 0);
-		} else {
+		else
 			sg_to_sec4_set_last(edesc->sec4_sg + sec4_sg_src_index -
 					    1);
-		}
 
+		if (*next_buflen)
+			scatterwalk_map_and_copy(next_buf, req->src,
+						 to_hash - *buflen,
+						 *next_buflen, 0);
 		desc = edesc->hw_desc;
 
 		edesc->sec4_sg_dma = dma_map_single(jrdev, edesc->sec4_sg,