crypto: chcr - Add ctr mode and process large sg entries for cipher

It send multiple WRs to H/W to handle large sg lists. Adds ctr(aes)
and rfc(ctr(aes)) modes.

Signed-off-by: Harsh Jain <harsh@chelsio.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>