metadata: fix seqnum on kernel notifications

metadata: fix seqnum on kernel notifications

The seqnum ID is passed together with the timestamps. Therefore, move the
"u64 seq" argument to kdbus_meta_add_timestamp(). As the seqnum is not
known at message allocation time, we now also move the
kdbus_meta_add_timestamp() to the time we actually allocate the ID.

This fixes seqnum IDs on kernel notifications.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>