gpg: Make OCB mode compliant in de-vs mode.

* g10/mainproc.c (proc_encrypted): Determine cipher mode and pass it
to the is_compliant test.

This patch also switches from just assuming CFB mode to passing the
correct mode to gnupg_cipher_is_compliant. Except for the legacy EAX
mode we only have these two modes and thus it does not really matter.
But correcting this is more future proof.

This was found while fixing
Backported-from-master: a73c88817ce2dc05d4eefc2a8f31b89504523a9a

The comliance.c part was already done in 2.2

• GnuPG-bug-id: T7804