crypto: ccree - use crypto_ipsec_check_assoclen()

Use crypto_ipsec_check_assoclen() instead of home grown functions.
Clean up some unneeded code as a result. Delete stale comments
while we're at it.

Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>