[dv/hmac] fix regression failure
[dv/hmac] fix regression failure

Hmac regression found one corner cases regarding fifo_empty.
After hash_process is issued, if message input is not a multiple
of 4, there is a period of time sequence won't check fifo_empty
interrupt because it is hard for scb to align.
Now since prim_packer can hold one more data, the ignored period of time
needs to be extended.

Signed-off-by: Cindy Chen <399ad771a111eac8923348b1e2af093034e5d4f1@google.com>

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