crypto: hash - Fix synchronous ahash chaining fallback

The synchronous ahash fallback code paths are broken because the
ahash_restore_req assumes there is always a state object.  Fix this
by removing the state from ahash_restore_req and localising it to
the asynchronous completion callback.

Also add a missing synchronous finish call in ahash_def_digest_finish.

Fixes: f2ffe5a9 ("crypto: hash - Add request chaining API")
Fixes: 439963cd ("crypto: ahash - Add virtual address support")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>