crypto: sun4i-ss - fallback when length is not multiple of blocksize

sun4i-ss does not handle requests when length are not a multiple of
blocksize.
This patch adds a fallback for that case.

Fixes: 6298e948 ("crypto: sunxi-ss - Add Allwinner Security System crypto accelerator")
Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>