cryptodev: Use 'csp' in the handlers for requests.

• Retire cse->mode and use csp->csp_mode instead.
• Use csp->csp_cipher_algorithm instead of the ivsize when checking for the fixup for the IV length for AES-XTS.

Reviewed by: markj
Sponsored by: Chelsio Communications, The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D32103

(cherry picked from commit b4e0a27c5be5090a9db16dd0ad417543b1fb0c4a)