FIX RTX 50XX Memory junction temp reading

* Update NvidiaGpu.cs
* Enhance 50 series detection logic

Author: sergiye

OpenHardwareMonitorLib/Hardware/Gpu/NvidiaGpu.cs

@@ -475,8 +475,17 @@ public override void Update()
 
             if (status == NvApi.NvStatus.OK)
             {
-                _hotSpotTemperature.Value = thermalSensors.Temperatures[1] / 256.0f;
-                _memoryJunctionTemperature.Value = thermalSensors.Temperatures[9] / 256.0f;
+                // RTX 50xx series
+                if (Name.StartsWith("NVIDIA GeForce RTX 50", StringComparison.OrdinalIgnoreCase))
+                {
+                    _hotSpotTemperature.Value = 0;
+                    _memoryJunctionTemperature.Value = thermalSensors.Temperatures[2] / 256.0f;
+                }
+                else
+                {
+                    _hotSpotTemperature.Value = thermalSensors.Temperatures[1] / 256.0f;
+                    _memoryJunctionTemperature.Value = thermalSensors.Temperatures[9] / 256.0f;
+                }
             }
 
             if (_hotSpotTemperature.Value != 0)