KEYS: revert encrypted key change

Commit fc7c70e0 "KEYS: struct key_preparsed_payload should have two
payload pointers" erroneously modified encrypted-keys.  This patch
reverts the change to that file.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: David Howells <dhowells@redhat.com>