Add a new COP_F_CIPHER_FIRST flag for struct crypt_op.

[jhb]

Summary

Add a new COP_F_CIPHER_FIRST flag for struct crypt_op.

This requests that the cipher be performed before rather than after
the HMAC when both are specified for a single operation.

Test Plan

• testing IPSec-like encrypt-then-authenticate operations from userland via the cryptocheck tool on ccr0 and cryptosoft
• encryption operations need this flag for EtA while decryption operations do not