iwlwifi: move plcp check to separated function

Move the plcp error checking into stand alone function and pointed by ops
to accommodate devices not needing this recovery.

Signed-off-by: Trieu 'Andrew' Nguyen <trieux.t.nguyen@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>