The cbc template should not be applied on stream ciphers, especially
ones that have internal state.  Enforce this by checking the state
size when the instance is created.

Reported-by:  <syzbot+050eeedd6c285d8c42f2@syzkaller.appspotmail.com>
Fixes: 47309ea1 ("crypto: arc4 - Add internal state")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>