kms: Print the screen virtual position in the logs

It is impossible to see otherwise what is going on.
What's worse, it prints the screen geometry (that does not
include the virtual desktop adjustment), which is incredibly
confusing.

Change-Id: Ie67a4d8110a0b5c9cb75e6290f06c857a980d2c8
Pick-to: 6.6
Reviewed-by: Christian Strømme <christian.stromme@qt.io>

src/platformsupport/kmsconvenience/qkmsdevice.cpp

@@ -716,6 +716,7 @@ void QKmsDevice::createScreens()
         // virtualIndex. This is not only handy but also required since for instance
         // evdevtouch relies on it when performing touch device - screen mapping.
         if (!m_screenConfig->separateScreens()) {
+            qCDebug(qLcKmsDebug) << "  virtual position is" << virtualPos;
             siblings.append(s);
             virtualPositions.append(virtualPos);
             if (orderedScreen.vinfo.isPrimary)