hx71x: Update api header and docs to correctly note "value" field

Update both hx71x and ads1220 to reflect that there is a third "value"
field in the reported data.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/extras/ads1220.py

@@ -69,9 +69,9 @@ class ADS1220():
             self.printer, self._process_batch, self._start_measurements,
             self._finish_measurements, UPDATE_INTERVAL)
         # publish raw samples to the socket
+        hdr = {'header': ('time', 'counts', 'value')}
         self.batch_bulk.add_mux_endpoint("ads1220/dump_ads1220", "sensor",
-                                         self.name,
-                                         {'header': ('time', 'counts')})
+                                         self.name, hdr)
         # Command Configuration
         mcu.add_config_cmd(
             "config_ads1220 oid=%d spi_oid=%d data_ready_pin=%s"

klippy/extras/hx71x.py

@@ -53,8 +53,8 @@ class HX71xBase():
             self._finish_measurements, UPDATE_INTERVAL)
         # publish raw samples to the socket
         dump_path = "%s/dump_%s" % (sensor_type, sensor_type)
-        self.batch_bulk.add_mux_endpoint(dump_path, "sensor", self.name,
-                                         {'header': ('time', 'counts')})
+        hdr = {'header': ('time', 'counts', 'value')}
+        self.batch_bulk.add_mux_endpoint(dump_path, "sensor", self.name, hdr)
         # Command Configuration
         self.query_hx71x_cmd = None
         mcu.add_config_cmd(