[kmac] Revise Assumption of process
[kmac] Revise Assumption of process

There was a corner case that can violate the assumption but which is
legitimate input. When msg_valid_i and process_i are asserted at the
sametime, and if the message is at the end of the block, the state
machine doesn't send the keccak_valid_o but triggers keccak_run_o and
wait the keccak complete in StMessageWait state. Then after return from
StMessageWait state, it proceed to StPad and send following
keccak_valid_o.

The assumption is revised to check end_of_block and process_latched

Signed-off-by: Eunchan Kim <cb7bc7ceb22698f298c67faa994fd9ddf3cab298@opentitan.org>

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