[sram/dv] Update scb
[sram/dv] Update scb

No real function update. Only remove unused functions and create a
function `reset_key_nonce` to reduce replication

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

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