ccr: Replace 'blkcipher' with just 'cipher'.

ccr(4) can handle requests for AES-CTR (a stream cipher), not just
block ciphers, so make the function and structure names more generic.

Sponsored by: Chelsio Communications

(cherry picked from commit 762f1dcb1c7ad6848a2f35a0b7397ef8fb91e28d)