crypto: factor out conversion of QAPI to gcrypt constants

The conversion of cipher mode will shortly be required in more
than one place.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
1 file changed