Macro dma_map_sg() may return 0 on error. This patch enables
checks in case of the macro failure and ensures unmapping of
previously mapped buffers with dma_unmap_sg().

Found by Linux Verification Center (linuxtesting.org) with static
analysis tool SVACE.

Fixes: 49186a7d ("crypto: inside_secure - Avoid dma map if size is zero")
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Reviewed-by: Antoine Tenart <atenart@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>