Fix slow status updates from the knx bus (#5963)

* Fix slow status updates from the knx bus

The data set in the entity was an array, not the value.

@fixes https://github.com/home-assistant/home-assistant/issues/4407

* speed up status update

homeassistant/components/knx.py

@@ -136,8 +136,8 @@ class KNXGroupAddress(Entity):
             information relating to this device.
             """
             if (addr == self.state_address) or (addr == self.address):
-                self._state = data
-                self.update_ha_state()
+                self._state = data[0]
+                self.schedule_update_ha_state()
 
         KNXTUNNEL.register_listener(self.address, handle_knx_message)
         if self.state_address: