iwlwifi: fix fw_restart module parameter

fw_restart module parameter was broken by the recent check for stuck
queue patch, driver check the fx_restart module parameter
before reload the firmware; but the stuck queue timer kick in after
firmware error and reload the firmware even fw_restart=0. In this case,
driver should not reload the firmware, it is important to help debugging
uCode error.

The only case we can ignore the module parameter is when user request
firmware reload from debugfs, which can bypass the checking and perform
firmware reload all the time.

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