[dv/kmac] fix CFG.entropy_ready exclusion
[dv/kmac] fix CFG.entropy_ready exclusion

This CSR field needs to be not written at all in any CSR test, otherwise
it has the potential to cause a whole assortment of strange issues
during simulation due to it kick-starting the entropy FSM.

Signed-off-by: Udi Jonnalagadda <790cd677b6a22a419ffcfe0eb4293d8866eb70c9@google.com>

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