dtrace: fix ipfw_rule_info_t translator

322e5efda8578b has changed field names in the struct ip_fw.
Use correct names in ipfw_rule_info_t translator in the ipfw.d script.

Reported by: Keith White <kwhite uottawa at gmail>

(cherry picked from commit 5c8e8e82aeaf3aa788acdd6cfca30ef09094230d)