Fix mysensors platforms version requirement (#5942)

* Notify and device tracker platforms require mysensors version 2.0 or
  greater.

homeassistant/components/device_tracker/mysensors.py

@@ -55,6 +55,8 @@ def setup_scanner(hass, config, see, discovery_info=None):
     gateways = hass.data.get(mysensors.MYSENSORS_GATEWAYS)
 
     for gateway in gateways:
+        if float(gateway.protocol_version) < 2.0:
+            continue
         gateway.platform_callbacks.append(mysensors_callback)
 
     return True

homeassistant/components/notify/mysensors.py

@@ -19,6 +19,8 @@ def get_service(hass, config, discovery_info=None):
         return
 
     for gateway in gateways:
+        if float(gateway.protocol_version) < 2.0:
+            continue
         pres = gateway.const.Presentation
         set_req = gateway.const.SetReq
         map_sv_types = {