Qnx: Inline only use of QnxDeviceFactory::deviceType()

And add a comment to the secondary use of Constants::QNX_QNX_OS_TYPE
as device type.

Change-Id: I1ae4bda890c87500a23e1df5cb7fa6e4f1079c96
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/qnx/qnxdevice.cpp

@@ -201,10 +201,5 @@ ProjectExplorer::IDevice::Ptr QnxDeviceFactory::create() const
     return wizard.device();
 }
 
-Core::Id QnxDeviceFactory::deviceType()
-{
-    return Core::Id(Constants::QNX_QNX_OS_TYPE);
-}
-
 } // namespace Internal
 } // namespace Qnx