added other bus options to the documentation

src/drivers/batt_smbus/batt_smbus.cpp

@@ -686,6 +686,8 @@ $ batt_smbus -X write_flash 19069 2 27 0
 
 	PRINT_MODULE_USAGE_COMMAND("start");
 	PRINT_MODULE_USAGE_PARAM_STRING('X', "BATT_SMBUS_BUS_I2C_EXTERNAL", nullptr, nullptr, true);
+	PRINT_MODULE_USAGE_PARAM_STRING('T', "BATT_SMBUS_BUS_I2C_EXTERNAL1", nullptr, nullptr, true);
+	PRINT_MODULE_USAGE_PARAM_STRING('R', "BATT_SMBUS_BUS_I2C_EXTERNAL2", nullptr, nullptr, true);
 	PRINT_MODULE_USAGE_PARAM_STRING('I', "BATT_SMBUS_BUS_I2C_INTERNAL", nullptr, nullptr, true);
 	PRINT_MODULE_USAGE_PARAM_STRING('A', "BATT_SMBUS_BUS_ALL", nullptr, nullptr, true);