This patch fixes mouse positioning with -device usb-tablet and fullscreen
or resized window.

Fixes: 46522a82
Signed-off-by: Jindrich Makovicka <makovick@gmail.com>
Message-Id: <20171117112258.5888-3-makovick@gmail.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>