ui/gtk: Update refresh interval after widget is realized

ui/gtk: Update refresh interval after widget is realized

Nikola reported on Windows when gd_vc_gfx_init() is called, the
window is not yet realized, so we run gd_refresh_rate_millihz(NULL)
which returns 0 milli-Hertz.
When a Widget is realized, it fires a 'realized' event. We already
have the gd_draw_event() handler registered for this even, so simply
move the gd_refresh_rate_millihz() there. When the event fires, the
window is known to exist.
This completes commit c4c00922cc original intention.

Reported-by: Nikola Pavlica <pavlica.nikola@gmail.com>
Tested-by: Nikola Pavlica <pavlica.nikola@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20200817172331.598255-1-philmd@redhat.com
Suggested-by: Nikola Pavlica <pavlica.nikola@gmail.com>
Tested-by: Nikola Pavlica <pavlica.nikola@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>