crypto: s5p-sss - fix incorrect usage of scatterlists api

sg_dma_len() macro can be used only on scattelists which are mapped, so
all calls to it before dma_map_sg() are invalid. Replace them by proper
check for direct sg segment length read.

Fixes: a49e490c ("crypto: s5p-sss - add S5PV210 advanced crypto engine support")
Fixes: 9e4a1100 ("crypto: s5p-sss - Handle unaligned buffers")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>