wip: try hacking in "write single register"

esphome/components/modbus_controller/modbus_controller.h

@@ -29,7 +29,7 @@ enum class ModbusFunctionCode {
   GET_COMM_EVENT_COUNTER = 0x0B,  // not implemented
   GET_COMM_EVENT_LOG = 0x0C,      // not implemented
   WRITE_MULTIPLE_COILS = 0x0F,
-  WRITE_MULTIPLE_REGISTERS = 0x10,
+  WRITE_MULTIPLE_REGISTERS = 0x06,
   REPORT_SERVER_ID = 0x11,               // not implemented
   READ_FILE_RECORD = 0x14,               // not implemented
   WRITE_FILE_RECORD = 0x15,              // not implemented