crypto: sun8i-ss - do not use sg_dma_len before calling DMA functions

When testing sun8i-ss with multi_v7_defconfig, all CBC algorithm fail crypto
selftests.
This is strange since on sunxi_defconfig, everything was ok.
The problem was in the IV setup loop which never run because sg_dma_len
was 0.

Fixes: 359e893e8a ("crypto: sun8i-ss - rework handling of IV")
Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/allwinner/sun8i-ss/sun8i-ss-cipher.c

@@ -141,7 +141,7 @@ static int sun8i_ss_setup_ivs(struct skcipher_request *areq)
 
 	/* we need to copy all IVs from source in case DMA is bi-directionnal */
 	while (sg && len) {
-		if (sg_dma_len(sg) == 0) {
+		if (sg->length == 0) {
 			sg = sg_next(sg);
 			continue;
 		}