iwlwifi: dbg_ini: add consecutive trigger firing support

When a dump trigger is fired, the driver sets IWL_FWRT_STATUS_DUMPING and
aborts any consecutive dump collection.
To allow consecutive triggers firing, use 5 dump workers and allocate
them upon incoming dump collection requests.

This functionality is needed since in ini debug mode each trigger may
have entirely different memory regions to collect unlike the legacy
mode in which all the triggers dump the same memory regions.

Signed-off-by: Shahar S Matityahu <shahar.s.matityahu@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>