1) in cm_isa_attach(), setup intr in the last step

1) in cm_isa_attach(), setup intr in the last step
2) in cm_attach()
   - after 1), cm_attach() is intr safe, remove crit-sect
   - initialize callout before cm_stop()
3) in cm_stop(), add missing callout_stop()
4) instead of clearing IFF_RUNNING immediately after every call of cm_stop(),
   move this clearing into cm_stop()