iwlwifi: don't perform "echo test" when cmd queue stuck

Perform "echo test" when cmd queue stuck detected, somethime it will cause
calltrace. I am not sure how to fix it yet, just remove the action now until
find a better way to handle it.

Reported-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>