iwlwifi: properly use delay option in dump trigger flow

Fix several issues related to dump delay:
1. In legacy dump trigger, use stop_delay field instead of trig_dis_ms.
2. ini delay is messured in usec so align both ini and legacy to usec.
3. schedule_delayed_work receives the delay value in jiffies so
translate the dump delay to jiffies.

Signed-off-by: Shahar S Matityahu <shahar.s.matityahu@intel.com>
Fixes: ea7cb829 ("iwlwifi: dbg: make trigger functions type agnostic")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>