iwlwifi: mvm: link to TX commands in documentation

Link from the TX_CMD enum value to the TX command structs.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
Signed-off-by: NLuca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/fw-api.h

@@ -215,7 +215,9 @@ enum iwl_legacy_cmds {
 	/* paging get item */
 	FW_GET_ITEM_CMD = 0x1a,
 
-	/* TX */
+	/**
+	 * @TX_CMD: uses &struct iwl_tx_cmd or &struct iwl_tx_cmd_gen2
+	 */
 	TX_CMD = 0x1c,
 
 	/**