Inverted the 'Device Already Open' check so it will work as designed. (#2095)

As per issue #2094
Co-authored-by: NGido Nijenhuis <g-nijenhuis@sensata.com>

src/devices/Ft232H/Ft232HI2cBus.cs

@@ -37,7 +37,7 @@ namespace Iot.Device.Ft232H
         /// <inheritdoc/>
         public override I2cDevice CreateDevice(int deviceAddress)
         {
-            if (!_usedAddresses.ContainsKey(deviceAddress))
+            if (_usedAddresses.ContainsKey(deviceAddress))
             {
                 throw new ArgumentException($"Device with address 0x{deviceAddress,0X2} is already open.", nameof(deviceAddress));
             }