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

[ Upstream commit 2dfc7cd7 ]

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: 359e893e ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>