This patch adds support for IPSec ESN (Extended Sequence Numbers) in
encrypt and authenticate mode (eg. AES-CBC and SHA256) and combined mode
(eg. AES-GCM).
For encrypt and authenticate mode the ESN is stored in separate crp_esn
buffer because the high-order 32 bits of the sequence number are
appended after the Next Header (RFC 4303).
For combined modes the high-order 32 bits of the sequence number [e.g.
RFC 4106, Chapter 5 AAD Construction] are part of crp_aad (prepared by
netipsec layer in case of ESN support enabled), therefore non visible
diff around combined modes.