[dv/keymgr_kmac_agent] Add 2 assertions to check last and done
[dv/keymgr_kmac_agent] Add 2 assertions to check last and done

Also fix some typos

Signed-off-by: Weicai Yang <4fa8c7762ee4da95e3dee7dae2c3263ea16637f9@google.com>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan