iwlwifi: dbg_ini: separate between ini and legacy dump flows

Separate between ini and legacy dump flows to allow adding ini triggers
that are not supported in the legacy flow and to increase readabilty.

iwl_fw_dbg_ini_collect function is now called with legacy trigger id and
_iwl_fw_dbg_ini_collect is called with ini trigger id.

Also make the actual dumping function static so that any dump collection
will go through iwl_fw_dbg_collect_sync.

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