crypto: acomp - Move stream management into scomp layer

Rather than allocating the stream memory in the request object,
move it into a per-cpu buffer managed by scomp.  This takes the
stress off the user from having to manage large request objects
and setting up their own per-cpu buffers in order to do so.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>