crypto: inside-secure - fix hash when length is a multiple of a block

This patch fixes the hash support in the SafeXcel driver when the update
size is a multiple of a block size, and when a final call is made just
after with a size of 0. In such cases the driver should cache the last
block from the update to avoid handling 0 length data on the final call
(that's a hardware limitation).

Cc: stable@vger.kernel.org
Fixes: 1b44c5a6 ("crypto: inside-secure - add SafeXcel EIP197 crypto engine driver")
Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>