Random replacement for HINT instructions
Created by: silabs-oysteink
Implemented random replacement for HINT instruction (c.slli with rd==x0 and immediate != 0).
Replacement instruction is taken from the random instruction generation within the dummy module. Hints are replaced by add/and/mul/bltu, but will show up on RVFI as c.slli.
Removed lfsr_lockup[0] as a cause of counter reset for the dummy module, as this could violate the dummy frequency.
Signed-off-by: Oystein Knauserud Oystein.Knauserud@silabs.com