iwlwifi: use .cfg to enable/disable continuous ucode trace

Instead of checking device type for enable/disable continuous ucode
trace function; put it in .cfg for better control and more
flexibilities.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>