Ios: Fix compiler warnings

- avoid deprecated API
- remove unused variable

Change-Id: I33850ea2dda523900ead191542eadf65338d5210
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/ios/iosdevice.cpp

@@ -486,7 +486,12 @@ void IosDeviceManager::monitorAvailableDevices()
         CFRelease( cfProductIdMaskValue );
     }
 
-    IONotificationPortRef notificationPort = IONotificationPortCreate(kIOMasterPortDefault);
+#if QT_MACOS_DEPLOYMENT_TARGET_BELOW(120000)
+    const mach_port_t port = kIOMasterPortDefault; // deprecated in macOS 12
+#else
+    const mach_port_t port = kIOMainPortDefault; // available since macOS 12
+#endif
+    IONotificationPortRef notificationPort = IONotificationPortCreate(port);
     CFRunLoopSourceRef runLoopSource = IONotificationPortGetRunLoopSource(notificationPort);
 
     CFRunLoopAddSource(CFRunLoopGetCurrent(), runLoopSource, kCFRunLoopDefaultMode);
@@ -495,16 +500,14 @@ void IosDeviceManager::monitorAvailableDevices()
     CFRetain(matchingDictionary);
 
     // Now set up a notification to be called when a device is first matched by I/O Kit.
-    kern_return_t kr;
+    IOServiceAddMatchingNotification(notificationPort,
-    kr = IOServiceAddMatchingNotification(notificationPort,
                                      kIOMatchedNotification,
                                      matchingDictionary,
                                      deviceConnectedCallback,
                                      NULL,
                                      &gAddedIter);
 
-
+    IOServiceAddMatchingNotification(notificationPort,
-    kr = IOServiceAddMatchingNotification(notificationPort,
                                      kIOTerminatedNotification,
                                      matchingDictionary,
                                      deviceDisconnectedCallback,