[dv, otbn] Adust the `scramble_test` to tolerate the right amount of false positives
[dv, otbn] Adust the `scramble_test` to tolerate the right amount of false positives

Signed-off-by: Douglas Reis <df95399f7253aef5711aa5e1f53e8824981313ab@lowrisc.org>

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