Android: Fix AVD display if there are no AVDs

Fix that a broken dummy item was shown in the AVD Manager tab in the
Android options, if no AVD is available.

Fixes: QTCREATORBUG-19338
Change-Id: I31550812c332ff78d107d79682e064aa9eae1070
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/android/androiddeviceinfo.h

@@ -55,6 +55,7 @@ public:
     bool isValid() const { return !serialNumber.isEmpty() || !avdname.isEmpty(); }
     bool operator<(const AndroidDeviceInfo &other) const;
     bool operator==(const AndroidDeviceInfo &other) const; // should be = default with C++20
+    bool operator!=(const AndroidDeviceInfo &other) const { return !(*this == other); }
 };
 using AndroidDeviceInfoList = QList<AndroidDeviceInfo>;