iwlwifi: remove duplicated debug functions

Use the show uCode statistics function for uCode debugging purposes only; it
is being duplicated in both debugfs and sysfs. remove the one from sysfs.

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