iwlwifi: mvm: document switch case fall-through in iwl_mvm_send_sta_key

Add a comment indicating that the WLAN_CIPHER_SUITE_WEP104 case falls
through to the WLAN_CIPHER_SUITE_WEP40 case in iwl_mvm_send_sta_key.
This will document that the lack of a break is intentional.

Coverity: CID 1260023
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/iwlwifi/mvm/sta.c

@@ -1196,6 +1196,7 @@ static int iwl_mvm_send_sta_key(struct iwl_mvm *mvm,
 		break;
 	case WLAN_CIPHER_SUITE_WEP104:
 		key_flags |= cpu_to_le16(STA_KEY_FLG_WEP_13BYTES);
+		/* fall through */
 	case WLAN_CIPHER_SUITE_WEP40:
 		key_flags |= cpu_to_le16(STA_KEY_FLG_WEP);
 		memcpy(cmd.key + 3, keyconf->key, keyconf->keylen);