Add controller buffer constants, finish misc battle doc

src/battle_controller_link_opponent.c

@@ -555,7 +555,7 @@ static void LinkOpponentHandleGetMonData(void)
             monToCheck >>= 1;
         }
     }
-    BtlController_EmitDataTransfer(1, size, monData);
+    BtlController_EmitDataTransfer(BUFFER_B, size, monData);
     LinkOpponentBufferExecCompleted();
 }