Improve AAD and GCM tag handling in cipher API

Improve AAD and GCM tag handling in cipher API

* AAD may also be a subject of backend chunk size limitation. Allow
  calling ckmc_cipher_init multiple time do provide consecutive AAD
  portions.
* When encrypted data is split in to chunks there's no way to locate
  the trailing GCM tag part. Add optional buffer argument to
  ckmc_cipher_finalize() to allow passing the tag explicitly. This
  function will also return the tag in the output buffer during
  encryption.

Change-Id: Ic9ddb86e294f8180fb44327c1f4ac4f4650b3e4c