korina: misc cleanup

- useless initialization (korina_ope / korina_restart)
- use a single variable for the status code in korina_probe
  and propagate the error status code from below
- useless checks in korina_remove : the variables are
  necessarily set when korina_probe succeeds

Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>