crypto: sun8i-ss - Use kfree_sensitive

The kfree_sensitive is a kernel API to clear sensitive information
that should not be leaked to other future users of the same memory
objects and free the memory. Its function is the same as the
combination of memzero_explicit and kfree. Thus, we can replace the
combination APIs with the single kfree_sensitive API.

Signed-off-by: Jason Wang <wangborong@cdjrlc.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>