iwlwifi: make sure cur_fw_img is valid before accessing img

Harden the fwrt->fw->img array access by making sure the cur_fw_img
value doesn't go out of bounds.
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/fw/dbg.h

@@ -381,6 +381,7 @@ static inline bool iwl_fw_dbg_is_paging_enabled(struct iwl_fw_runtime *fwrt)
 {
 	return iwl_fw_dbg_type_on(fwrt, IWL_FW_ERROR_DUMP_PAGING) &&
 		!fwrt->trans->cfg->gen2 &&
+		fwrt->cur_fw_img < IWL_UCODE_TYPE_MAX &&
 		fwrt->fw->img[fwrt->cur_fw_img].paging_mem_size &&
 		fwrt->fw_paging_db[0].fw_paging_block;
 }